et al citation in research paper

How Do You Use et al. in Scientific Papers? (with many examples)

Et al. in academic writing helps you cite a publication with multiple contributors. Exactly how and where to use it varies depending on the specific journal publication or prescribed style guide. Even experienced authors have trouble with “et al.” Here we help clarify its use across every major style guide.

Updated on June 15, 2022

In scholarly papers, citation rules definitely have some strange terms. Some aren't English, and some aren't words. The term “et al.”, for instance, isn't an English word. For someone who speaks a non-Latin-origin language, like Japanese or Arabic, it's especially confusing. This post explains the use of et al. and some common mistakes related to it.

You use “et al.” in academic writing to cite a publication that has multiple authors (or other contributors, such as editors). For example, instead of an in-text citation reading (Schouten, McAlexander, Smith, Rogers, & Koenig 2010), it would simply be (Schouten et al., 2010).

Et al. is used in manuscript body text and in reference lists and footnotes. Exactly how and where to use it varies depending on the prescribed style, such as APA, AMA, Harvard, Vancouver, or that of a specific publication. It's short for et alia (or the respective masculine and feminine plural et alii or et aliae) – Latin for “and others.” The abbreviation is required, but it also makes writing easier to read, helping the reader find the cited works faster.

Even experienced authors have trouble with “et al.” because many major academic writing style guides, as well as specific journals, use it slightly differently. Let's look at the main ones you'll typically see when you're seeking to publish your scientific manuscript. Some of these styles are updated regularly, so always be sure to check with your professor and/or with your target publication's guidelines.

Using et al. in the main academic referencing styles

The following sections will show how to use “et al.” in APA, MLA, Vancouver, and other main referencing styles, especially those found in journals.

APA (American Psychological Association) Style

APA is commonly used in the social sciences and medicine, both in universities and in publications. Keep up to date on the latest APA style as well.

For in-text citations in APA Style , when a source has two authors, list both authors by their last names, followed by the publication year. For three or more authors, cite the first author followed by “et al.”

Note that these rules are based on the Publication Manual of the American Psychological Association, Seventh Edition (APA 7). The previous versions required listing more authors in the in-text citations, and had some differences in the reference list requirements.

APA Style in-text citations

The main difference in APA Style in-text citations is their use of the ampersand (&) symbol. Et al. is now simply used for three-plus authors. It used to be more confusing, as up to five authors were listed at first reference and then et al. on second reference. Many will not be familiar with the current style, so be sure to check.

APA Style reference list

The “et al.” abbreviation is not used in the APA references list. But knowing how to prepare the list can help you know when to use et al. in the in-text citations.

For publications with 3–20 authors put all the authors. For example:

Eckhardt, G., Houston, M., Jiang, B., Lamberton, C., Rindfleisch, A. & Zervas, G. (2019). Marketing in the sharing economy. Journal of Marketing , 83(5), 5-27.

For a source with 20 or more authors put the first six authors, followed by an ellipsis (…) and then the final author. For example:

Pegion, K., Kirtman, B. P., Becker, E., Collins, D. C., LaJoie, E., Burgman, R., . . . Kim, H. (2019). The subseasonal experiment (SubX): A multimodel subseasonal prediction experiment. Bulletin of the American Meteorological Society , 100(10), 2043-2061.

APA Style is rather idiosyncratic with its combinations of spaces and commas. Be careful with those, especially if you have a picky adviser or run into a picky peer reviewer or journal editor.

MLA (Modern Language Association) Style

MLA Style is most commonly used in the humanities. Nothing makes it especially unique, but it has its own slight differences.

MLA Style in-text citations

Unlike APA Style, MLA Style doesn't use the year in the citation. Instead, it uses the authors' last names and the relevant page number.

Use “et al.” for sources with three or more authors for both in-text citations and in the references list.

MLA Style reference list

For the reference list, known as the Works Cited list in MLA Style, publications with three or more authors will look like this:

Wysocki, Anne Frances, et al. Writing New Media: Theory and Applications for Expanding the Teaching of Composition . Utah State University Press, 2004.

Vancouver Style

The Vancouver Style guide was developed in Canada by the International Committee of Medical Journal Editors (ICMJE) . It's now widely used for journal referencing in medicine, health sciences, and life sciences, and even in technology.

It's a concise style that works well for hyperlinking and with referencing software such as EndNote.

Vancouver Style in-text citations

Vancouver Style uses numbers for in-text citations, so using “et al.” is not a concern. However, if an author is named in a sentence, use “et al.” for publications with more than one author. For example:

“Holt et al. found that there was no histochemical evidence of mitochondrial myopathy.”

Vancouver Style reference list

For the reference list, put the names of up to six authors. For example:

Holt IJ, Miller DH, Harding AE. Genetic heterogeneity and mitochondrial DNA heteroplasmy in Leber's hereditary optic neuropathy. J Med Genet. 1989 Dec; 26 (12): 739-743 .

For seven or more authors put the first six and “et al.” For example:

Meakin CJ, King DA, White J, Scott JM, Handley H, Griffiths A, et al. Screening for depression in the medically ill. J Nerv Ment Dis 1991; 12: 45‐53 .

AMA (American Medical Association) Style

Also very common in medical referencing is AMA Style. AMA Style tends to be used for strictly clinical medical journals and the life sciences.

AMA Style In-text citations and reference list

The AMA system is similar to the Vancouver system in that it also uses numbers for in-text citations. The difference is found in the way AMA treats publications with seven or more authors in the reference list.

In AMA put the names of all the authors for up to six authors. For example:

Mizumoto K, Kagaya K, Zarebski A, Chowell G. Estimating the asymptomatic proportion of coronavirus disease 2019 (COVID-19) cases on board the Diamond Princess cruise ship, Yokohama, Japan, 2020. Euro Surveill. 2020;25(10):2000180.

For seven or more authors put the first three, followed by “et al.” For example:

Ahn DG, Shin HJ, Kim MH, et al. Current Status of Epidemiology, Diagnosis, Therapeutics, and Vaccines for Novel Coronavirus Disease 2019 (COVID-19). J Microbiol Biotechnol. 2020;30(3):313-324.

Chicago/Turabian Style

Chicago Style (and the very similar Turabian Style) is an American English style guide that is widely used in books in the social sciences and humanities, as well as journalism. It's less commonly used in journals.

The massive and comprehensive book called The Chicago Manual of Style (CMOS) has two referencing systems: author-date and notes and bibliography (which, by the way, LaTex can handle automatically).

Chicago Style in-text citations

Use of “et al.” is the same in both of the above referencing styles. For in-text citations put all last names when there are up to three authors. For four or more authors put the first author's name followed by “et al.”

For footnotes, but the full author name(s). Note that relevant page numbers are also usually given in Chicago Style. Also, unlike APA Style, the word “and” is used instead of the & ampersand symbol. Footnotes are usually indicated in the text with a superscript number.

Chicago Style reference list

For the reference list in Chicago Style, use all authors' full names if the source has up to 10 authors. For example:

Sechzer, Jeri A., S. M. Pfaffilin, F. L. Denmark, A. Griffin, and S. J. Blumenthal, eds. Women and Mental Health . Baltimore: Johns Hopkins University Press, 1996.

For more than 10 authors put the first seven, followed by “et al.”

Harvard Style

This style guide will be familiar for students who have studied in the US or under US professors. It's commonly used from the high school level upward. It's less common in scientific publications.

Harvard Style in-text citations

For in-text citations in Harvard Style put all names if the source has three or fewer authors. Use “et al.” if there are four or more authors. Just to make things even more confusing, Harvard usually does not put a comma between the author name or between “et al.” and the year.

Harvard Style reference list

For the reference list in Harvard Style put the names of all the authors, no matter how many there are. For example:

Lupien, S.J., McEwen, B.S., Gunnar, M.R. and Heim, C., 2009. Effects of stress throughout the lifespan on the brain, behaviour and cognition. Nature Reviews Neuroscience , 10(6), pp. 434-445.

Harvard style is primarily used in university settings, and each school may have its own variations. Be sure to check, because Harvard shows a lot of variety in punctuation and capitalization depending on the university or publication using it.

Specific journal variations

Despite the great number of referencing styles available, some journals prefer to use their own style of referencing. These are almost never 100% unique. Most often, they are based on a popular style, but with a few alterations.

Most commonly, Vancouver Style is used as a basis for making a publication's or journal's “house style” (see more on that topic below). Some add spaces. Some change the punctuation. Some use superscript numbers while others use numbers in parentheses or brackets.

For instance, the popular online open-access (OA) journal PLOS ONE states it uses Vancouver Style. It does, but it also places citation numbers in brackets and it removes spaces in some punctuation in the reference list. These are small differences, but an author must do them correctly or they risk having their submission rejected by their target journal .

Another example, the American Society of Agricultural and Biological Engineers (ASABE) , which produced journals including Transactions of the ASABE , uses a variation of APA Style 6th Edition. Why? We may never know. But if you're submitting to them, you must follow their guidelines.

To be sure you satisfy the guidelines you can hire a professional scientific editor who has done this task hundreds, even thousands, of times. We're skilled at spotting tiny differences in styles. It's part of an editor job.

Common mistakes in using et al. in academic writing

There are several common mistakes that authors of any level should be aware of when using et al.

Using et al. when you shouldn't

Knowing where you should and should not put et al. depends on the style guide you're following. That's all. However, some authors simply put use et al. when there's more than one author. That's just wrong.

The recent APA Style update also made things confusing for students and publication-seeking researchers, because some professors and journal reviewers will be following APA 6 while others will be updated to APA 7. Still others may not care. If you're not sure, ask.

Using the period in et al.

Maybe the most common problem in using et al. is knowing where to put the period. It should be after the “al.” and not after the “et”. This is because, as mentioned, “et al.” is an abbreviation of the Latin phrase “et alia.” The “et” is itself a word.

The “et al.” may be followed by any other punctuation. For example:

(Aaker et al., 2004)

Or it may not. It depends on the publication.

When et al. ends a sentence, use only one period. For example:

“This leads to a 40% reduction in food waste, as shown by Simpson et al.”

“Et al.” vs. “etc.”

“Et al.” and “etc.” are sometimes confused with each other. But they're completely different.

The abbreviation “et al.” is used for lists of authors (or other contributors). That's all. However, “etc.” ( et cetera , which is the Latin word for “and other similar things”) is used for lists or related items. For example:

“Riches et al. (2017) suggest that subcultures form around a variety of popular music styles (punk, hip hop, etc.), each with its own aesthetics and ethos.”

Final words on et al.

Although the basic concept behind using “et al.” is easy, each system is different. For journal submission, check the specifics. The journal may use a common style such as APA or Vancouver, but with a few custom differences. Some journals are very picky about this, some are not.

Even though the abbreviation is required, it adds readability. Modern scientific writing should be accessible and readable; so et al., though tricky, is a good thing .

If you need formatting for your manuscript to be sure you're using the right guidelines, scientific editors can do that for you. Journal guidelines are notoriously quirky and if English isn't your first language, they're even harder.

Professional scientific editors are trained in dealing with this. Many of us even enjoy it! Get a professional edit if you want to be sure you have your references totally consistent and pleasing to the journal editor's discerning eyes.

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How to Use ‘‘et al.’’ in APA Style (7th Edition)

The term ‘‘et al.’’ is the abbreviated form of the Latin term ‘‘et alia,’’ which means ‘‘and others.’’ It is used in academic in-text citations when referring to a source with multiple authors. In APA style, for a source with three or more authors, list the first author’s last name and “et al.” for all citations, including the first citation.

The Term ‘‘et al.’’ is the Abbreviation of Latin Term ‘‘et elia,’’ Meaning ‘‘and others’’

The term ‘‘et al.’’ is the abbreviated form of the Latin term ‘‘ et alia,’’ which means ‘‘and others.’’ It is used in academic in-text citations when referring to a source with multiple authors. In APA style, for a source with three or more authors , list the first author’s last name and “et al.” for all citations, including the first citation. Note that this rule has changed from APA 6th edition guidelines on using ‘‘et al.’’  which recommend listing all author names in the first citation up to five authors but then using ‘‘et al.’’  for the second and subsequent citations.

In October 2019, the American Psychological Association (APA) introduced the 7th edition of the APA Publication Manual, which replaces the 6th edition. The in-intext citation for works with three or more authors is now abbreviated right from the first citation. You only include the first author’s name and  “et al.”

For two authors: Always cite both authors' names in-text everytime you reference them.

Here is how this would look for a source authored by Parker, Robin, and Williams published in 2018.

( Parker et al., 2018)

            or

Parker et al. (2018) claimed that…

Note that there will be no comma between the surname and  ‘‘et al.’’  but a comma should be placed before the date in parentheses citation.  Also, the period goes only after the  ‘‘al.’’     even when it falls in the middle of a sentence.

The Correct Use of ‘‘et al.’’

Authors make several mistakes when using ‘‘et al.’’ in academic writings. The “al” in “et al.” is always followed by a period because the period shows that it is the abbreviated form of the term ‘‘et alia.’’

Thus, the following forms are not correct: ‘‘ et al’’, ‘‘et. al’’, ‘‘et. al.’’

The proper use of the abbreviation is ‘‘et al.’’

Also, “et al.” can be directly followed by another punctuation where necessary. However, the period always comes first:

(Parker et al., 2018)

When “et al.” is used right at the end of a sentence, only one period is used:

... by Parker et al. (2018)

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For more information about the citation styles and APA style, read the following articles:  

The 9 Most Important Changes in the 7th Edition of the APA Manual

APA Manual 7th Edition: In-Text Citation

How to Present Tables and Figures in APA Style (7th edition)

How to Use et al. in APA Style (7th Edition)?

APA Style: In-Text Citation | Reference List Entry

How to Cite Sources in APA Referencing Style? | With APA 7th Edition Update

How and When to Use ”et al.” in APA In-Text Citations?

Citation Styles | Which Citation Style Should I Use?

APA Formatting Guide for Academic Manuscripts

This handout discusses how and when to use et al. in APA style (7th edition). To give you an opportunity to practice your proofreading, we have left a few spelling, punctuation, or grammatical errors in the text. See if you can spot them! If you spot the errors correctly, you will be entitled to a 10% discount.

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When you are writing for academic purposes, you need to keep a ton of rules and regulations in mind. However, that is not the whole story, as you also need to keep the style guide in mind. While writing for academic work is not easy, nothing can be impossible with practice. Therefore, we are here with a compact citation style guide that abides by academic standards. If you are new to editing and proofreading or new to the academic side, this article will help you learn about the 8 most common citation styles used in academic writing.

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When to Use Author “et al.” in Citation and References

We publish because we want to share our knowledge and because we want recognition for our work. We acknowledge people’s ideas and findings by providing citations. Unfortunately, however, the rules regarding this common practice are not always easy to decipher, even for the best of us! We have published a number of other articles that help you navigate citation requirements, for example on the best citation format for science papers, how many references you should include in your research paper, and the general differences between common citation styles .

This article focuses on how to name the authors of cited works, including when to use the abbreviated Latin term “et al.” that usually accompanies the phrase “author et al.” Please make sure to follow the relevant journal guidelines concerning punctuation, citation style, etc., as publishers do not always follow the exact same formatting rules. Let’s start with some general definitions, and then look at specific rules of the most common style guides .

Table of Contents:

• What are the main types of citations? 
• Why do we use “et al.” in citations? 
• Using “et al.” vs “etc.”
• When Do We Use “et al.” in Citations? 

How to Cite “et al.” in APA Style

• How to Cite “et al.” in Chicago
• How to Cite “et al.” in MLA Citations

What are the main types of citations?

When referring to published literature, you need to provide details so that others can find and review the original material you base your ideas and claims on. In your research paper, you can make references to source materials using either endnotes and footnotes (i.e., numbers in the text that refer to the bottom of the page or the end of the paper) or in-text citations. Both styles require you to also provide a reference list at the end of the document.

In-text (or parenthetical) citations

When referencing other literature by author name or title in the text paragraphs of your paper, you are using in-text citations . Another similar method of citing is using parenthetical citations , as the referencing information is usually placed within parentheses. Both of these citation types are common in APA style.

Endnotes and footnotes

Endnotes and footnotes help declutter your writing. They are simple notation systems that allow you to use numbers in the body of a text to reference a cited work. Each number corresponds to further information or a citation entry found at the end of a manuscript (for endnotes) or at the bottom of the page where the cited reference is mentioned (for footnotes).

Footnotes are rarely found in scientific writing but are frequently used in the humanities and social sciences. Additionally, endnotes often replace parenthetical in-text citations in scientific journals these days – make sure you pay attention to the journal guidelines when you prepare your manuscript so that you don’t have to suddenly change your entire citation style before submitting or during the review process.

Reference lists

A reference list compiles all the works cited within a document for ease of reference and is included at the end of a manuscript. It must be included regardless of how the source material is acknowledged within the main body of your article. The author guidelines of your target journal will tell you whether the list has to be ordered alphabetically or in order of appearance in the text (when using a numbered system), and what general style it has to adhere to.

Why do we use “et al.” in citation?

The Latin term “et al.” is short for “et alii” and means “and others.” The abbreviation is used when citing a source with multiple authors. Its function is similar to that of “et cetera”, another common Latin phrase that is usually abbreviated as “etc.” and means “and other similar things.”

Using “et al.” vs “etc.” in Citation and References

As stated above, “et al.” is used strictly when talking about people, while “etc.” is only used for things. Apart from this key difference, they have the same function: replacing a list.

When to Use “et al.” in Reference and Citation

We cannot stress this enough, but always double-check your journal or relevant style guide regarding Latin terms and citations. There is no uniform rule on when to use “et al.”, but at least the phrase’s spelling is consistent. Always write “et al.” in lowercase and include a period after “al.”, even when it appears in the middle of a sentence.

The abbreviation “et al.” replaces author names in endnotes, footnotes, and in-text citations; it depends on the target journal whether “author et al.” citation style can also be used in the reference list or whether all author names need to be spelled out in that section . In the following section, you will find further information on how to cite references according to the most common citation styles and examples.

The APA style is frequently used in social science publications. Examples of book and journal citations are provided below. For information about other sources and special cases, see the Publication Manual of the American Psychological Association , Seventh Edition (2020) .

In-text or parenthetical citations (author-date system)

APA style uses the author-date notation, and the in-text citation rules apply to both digital and print editions of books and journals. Also, while providing page number references is optional for paraphrased statements, the APA recommends including them. Also, note that APA style uses the ampersand (&) to list author names in parentheses.

The same author rules apply to all source media including books, print periodicals, electronic journals, etc. Also, since reading electronic journals has become the norm for academics, the APA recommends including a DOI number for each journal article referenced, even if you accessed the document in print. Do not include a period (.) after the DOI information. Also note that APA reference lists should not contain “et al.”, and that the author-number thresholds for formatting rules in the reference list are different from those for in-text citations specified above.

The APA style does not use footnotes and strongly discourages the use of endnotes, which should only provide tangential information. However, sometimes content notes are necessary. In such cases, use the notation covered in Section 2.12 of the  APA Publication Manual .

How to Cite “et al.” in Chicago Style

The Chicago style is commonly used in the humanities. Below, we only comment on general book and journal citation formats. For additional information, see Wordvice’s guide on the Chicago Manual of Style , 17th edition . For an example of an annotated paper that uses bibliographic notation (i.e., numbers that refer to sources in a list), see the Pu rdue Owl’s NB sampler. See an example of an author-date paper.

Note that for formally published online sources, such as electronic academic journals, you do not need to include access date information except if required by your publisher or discipline. If no DOI is available, provide the uniform resource locator (URL). Unlike APA style, Chicago style does NOT use the ampersand (&) in name lists; instead, use “and.” Additionally, an author’s given names (first and middle) should be written in full (no initials) unless the author consistently publishes using initials.

Using “et al.” in in-text or parenthetical citations (author-date system)

Parenthetical citations are more commonly adopted by authors in the social, physical, and natural sciences. The same notation is used for digital and print editions of books and journals.

Don’t use “et al.” in reference lists

Using author “et al.” in books

Using author “et al.” in journals

Using “et al.” in endnotes and footnotes (bibliographic system)

How to cite “et al.” in mla style.

The MLA style is commonly used by writers in the humanities. General book and journal citation formations are highlighted below. For information regarding other media and special cases, see Wordvices guide on the MLA Handbook style rules .

Using “et al.” in in-text (parenthetical) citations

The MLA style uses an author-page style instead of an author-date style.

Using “et al.” in the reference list (works cited page)

Using “et al.” in endnotes and footnotes.

The MLA style does not generally encourage endnotes and footnotes; however, it does accommodate their use when needed to clarify points that don’t otherwise belong in the main body of your work. The formats for these notes are similar to the format used for in-text citations, but without the parentheses:

One author : See [last name] [page range]

See Johnson 5-15 for a further discussion of this phenomenon.

Multiple authors/studies:  

[Comment]. See [last name] [page range], [last name] [page range], [last name] [page range]

Several other studies make the same argument. See, for example, Walker and Francis 112-118, Thomson 20-43, and Muller 78-90.

Regarding [content topic], see [last name] [page range] and [last name] [page range]; for [content topic], see [last name] [page range], [last name] [page range], and [last name] [page range].

Regarding this phenomenon’s impact on trauma caretakers, see Miller 54-68 and Willis 23-25; for alternative explanations, see Jones 23-25, Thompson 64-55, and Smith 12-15.

Using Academic Editing Services to Prepare Your Paper

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APA In-Text Citations (7th Ed.) | Multiple Authors & Missing Info

Published on November 4, 2020 by Raimo Streefkerk . Revised on September 30, 2022.

In-text citations briefly identify the source of information in the body text. They correspond to a full reference entry at the end of your paper.

APA in-text citations consist of the author’s last name and publication year. When citing a specific part of a source, also include a page number or range, for example (Parker, 2020, p. 67) or (Johnson, 2017, pp. 39–41) .

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Table of contents

Apa in-text citations explained in 4 minutes, parenthetical vs. narrative citations, apa in-text citations with multiple authors, no author, date or page number, multiple sources in one parenthesis, avoiding ambiguity in apa in-text citations, citing indirect sources (“as cited in”), citing personal communication, general mentions of websites and software, example paragraph with in-text citations, frequently asked questions.

The in-text citation can be placed in parentheses or naturally integrated into a sentence.

• Parenthetical : There is a correlation between social media usage and anxiety symptoms in teenagers (Parker, 2019) .
• Narrative: Parker (2019) found a correlation between social media usage and anxiety symptoms in teenagers.

The publication year appears directly after the author’s name when using the narrative format. The parenthetical citation can be placed within or at the end of a sentence, just before the period. Check out a full example paragraph with in-text citations .

If a work has two authors, separate their names with an ampersand (&) in a parenthetical citation or “and” in a narrative citation. If there are three or more authors, only include the first author’s last name followed by “et al.”, meaning “and others”.

Group authors known by their abbreviations (e.g., CDC) are written in full the first time and are abbreviated in subsequent citations.

If the author of a source is unknown, try to determine if there is an organization or government responsible for creating the content. If so, include its name in the in-text citation (and reference entry).

Alternatively, use the source title in place of the author. Italicize the title if it’s italicized in the reference entry (except for court cases , which are italicized in the in-text citation but not the reference entry). Otherwise, enclose it in double quotation marks.

Apply title case capitalization, and shorten long titles. The first word of the title should always be included so readers can easily locate the corresponding reference entry.

• (“U.S. Flood Risk,” 2015)
• ( Thinking, Fast and Slow , 2017)

No publication date

If the publication date is unknown, write “n.d.” (no date) in the in-text citation.

No page number (alternative locators)

Page numbers are only required with direct quotes in APA . If you are quoting from a work that does not have page numbers (e.g., webpages or YouTube videos ), you can use an alternative locator, such as:

• (Liu, 2020, 03:26 )
• (Johnson, 2019, Chapter 3 )
• (McCombes, 2016, para. 4 )
• (Davis, 2016, Slide 15 )
• (Flores, 2020, Table 5 )
• (Streefkerk, 2020, “No page number” section )

Note that Bible citations always use chapter and verse numbers, even when page numbers are available:

If a statement is supported by multiple sources, the in-text citations can be combined in one parenthesis. Order the sources alphabetically, and separate them with a semicolon.

When citing multiple works from the same author, list the years of publication separated by a comma.

When in-text citations are ambiguous because they correspond to multiple reference entries, apply the solutions outlined in the table below.

If you want to refer to a source that you have found in another source, you should always try to access the original or primary source .

However, if you cannot find the original source , you should cite it through the secondary source that led you to it, using the phrase “as cited in”.

If the publication date of the primary source is unknown, include only the year of publication of the secondary source.

Only include a reference entry for the secondary source, not the primary source.

Personal communications , such as phone calls, emails, and interviews, are not included in the reference list because readers can’t access them. The in-text citation is also formatted slightly differently.

Include the initials and last name of the person you communicated with, the words “personal communication,” and the exact date in parentheses.

General mentions of a website or software don’t have to be cited with an in-text citation or entry in the reference list. Instead, incorporate relevant information into the running text.

• The website of Scribbr (www.scribbr.com) contains various useful resources.
• Statistical software SPSS (version 25) was used to analyze the data.

When citing a webpage or online article , the APA in-text citation consists of the author’s last name and year of publication. For example: (Worland & Williams, 2015). Note that the author can also be an organization. For example: (American Psychological Association, 2019).

If you’re quoting you should also include a locator. Since web pages don’t have page numbers, you can use one of the following options:

• Paragraph number: (Smith, 2018, para. 15).
• Heading or section name: ( CDC, 2020, Flu Season section)
• Abbreviated heading:  ( CDC, 2020, “Key Facts” section)

Instead of the author’s name, include the first few words of the work’s title in the in-text citation. Enclose the title in double quotation marks when citing an article, web page or book chapter. Italicize the title of periodicals, books, and reports.

If the publication date is unknown , use “n.d.” (no date) instead. For example: (Johnson, n.d.).

The abbreviation “ et al. ” (meaning “and others”) is used to shorten APA in-text citations with three or more authors . Here’s how it works:

Only include the first author’s last name, followed by “et al.”, a comma and the year of publication, for example (Taylor et al., 2018).

Always include page numbers in the APA in-text citation when quoting a source . Don’t include page numbers when referring to a work as a whole – for example, an entire book or journal article.

If your source does not have page numbers, you can use an alternative locator such as a timestamp, chapter heading or paragraph number.

If you cite several sources by the same author or group of authors, you’ll distinguish between them in your APA in-text citations using the year of publication.

If you cite multiple sources by the same author(s) at the same point , you can just write the author name(s) once and separate the different years with commas, e.g., (Smith, 2020, 2021).

To distinguish between sources with the same author(s) and  the same publication year, add a different lowercase letter after the year for each source, e.g., (Smith, 2020, 2021a, 2021b). Add the same letters to the corresponding reference entries .

In an APA in-text citation , you use the phrase “ as cited in ” if you want to cite a source indirectly (i.e., if you cannot find the original source).

Parenthetical citation: (Brown, 1829, as cited in Mahone, 2018) Narrative citation: Brown (1829, as cited in Mahone, 2018) states that…

On the reference page , you only include the secondary source (Mahone, 2018).

An APA in-text citation is placed before the final punctuation mark in a sentence.

• The company invested over 40,000 hours in optimizing its algorithm (Davis, 2011) .
• A recent poll suggests that EU membership “would be backed by 55 percent of Danish voters” in a referendum (Levring, 2018) .

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How to Use Et Al. Effectively in Your Research Paper

Discover how to use et al correctly and easily with this step-by-step guide. Learn the rules and examples of using et al in academic writing.

Academic writing is full of various citation styles and abbreviations, and one of the most commonly used ones is “et al.” But what does it really mean, and how should you use it? 

When there are three or more writers, this Latin phrase, short for “et alia,” is used instead of mentioning all of them. While it may appear simple, correctly using “et al.” can be difficult, and many writers struggle to understand when and how to use it.

This article will go over everything you need to know about utilizing “et al.” in your research paper, from what it is to how to cite it.

What Is Et Al.? 

“Et al.” is a common acronym in academic writing to denote the presence of other writers who are not expressly mentioned. It comes from the Latin phrase “et alia” (which means “and others” in English). The use of Latin terms in academic writing extends back to the medieval period when Latin was the main scholarly language in Europe.

When a source contains three or more authors, it might be difficult to list all of them in a citation, especially when there is a large list of authors. In these specific situations, “et al.” might be used to indicate the presence of other authors who are not identified.

It’s worth noting that the use of “et al.” differs based on the citation style. In certain styles, such as APA and Chicago , “et al.” is used for sources with three or more authors, however, in MLA style, “et al.” is only used for sources with four or more writers in others.

How To Use Et Al.?

Here are some guidelines for effectively using “et al.” in academic writing:

• Use “et al.” when a source has a large list of authors: When there are several authors of a source, the term “et al.” is used to shorten the citation, and it is commonly used when there are three or more writers; nevertheless, verify your citation style guidelines. 
• After the first author’s name, add “et al.” Most citation styles, including APA and MLA, include “et al.” after the first author’s name in the citation. 
• The period should come after “al.”. For instance, “Smith et al.” is correct, however, “Smith et. al” is wrong.
• In academic writing, “et al.” is italicized but not capitalized. 
• Understand the citation style guidelines: The use of “et al.” varies depending on the citation style. Make sure to follow the citation style guidelines specified for your academic writing.

In general, “et al.” is a useful abbreviation that simplifies citations in research papers, and mastering its correct usage is crucial for producing clear and precise academic writing.

Et Alibi, Et Alii, And Others

One important piece of information concerning et al. is the different forms it may take. Here’s some more information on all the different forms of “et al.” and their meanings:

Et alia is the most fundamental and widespread form of “et al.” in academic writing, meaning “and others.” When the number of authors of a source exceeds the maximum allowed by a citation style, this phrase is commonly used in citations to denote multiple authors.

Et Alibi 

Another Latin term for “and elsewhere.” It is used to highlight that further information about a topic is available from another source or location. For example, if you’re referencing a source and there’s more material on the same issue in another source, you might say “et alibi” to indicate that other sources are available. 

In Latin, this is the feminine plural form of “et al.” It is used to show that a source has numerous female authors. For instance, if a source includes numerous female authors and you wish to highlight this in your citation, you may use “et aliae” rather than “et al.”

In Latin, this is the male plural form of “et al.” It is used to show that a source has numerous male authors. For instance, if a source includes numerous male authors and you wish to highlight this in your citation, you may use “et alii” rather than “et al.”

Difference Between Et Al. And Etc.

Et al. and etc. are two separate abbreviations used in academic writing.

Et al. is an abbreviation of the Latin term “et alia,” which translates as “and others.”, as previously stated. It is used in citations to show many authors of a source and is usually used amid a citation, after the first author’s name. Simply put, you may use “et al.” to indicate that there are other authors aside from the name mentioned. 

Etc. is an abbreviation of the Latin term “et cetera,” which means “and so forth” or “and other things.” It is used to show that a list of things extends beyond those specifically mentioned. For instance, if you’re presenting several examples of a specific topic, you may use “etc.” to show that there are more examples. The expression “Etc.” is commonly used at the conclusion of a list and is preceded by a comma. It is frequently followed by a period and, depending on the citation style, italicized.

In summary, “et al.” indicates numerous authors of a source in a citation, whereas “etc.” indicates a continuation of a list of items.

Common Mistakes

• Using “et al.” to indicate a list continuation: As previously stated, “et al.” should be used to denote multiple authors of a source and should not be used to suggest a list continuation.
• Using “etc.” to denote many authors: “Etc.” should never be used to denote multiple authors of a source. This is the responsibility of “et al.” and using “etc.” instead is considered wrong and deceptive.
• Capitalizing “et al.” and “etc.”: Both “et al.” and “etc.” are abbreviations and should be written in lowercase characters, unless at the beginning of a phrase.
• Using “and others” instead of “et al.”: It is more suitable in academic writing to use “et al.” instead of “and others” to denote multiple authors of a source. Using “and others” can be informal and may violate the citation style.
• Using “et cetera” instead of “etc.”: The acceptable abbreviation for “et cetera” is “etc.” and should be used instead. Using the entire sentence may be considered needless, and it may also take up precious space in a citation or text.

How To Cite Et Al.

Here’s how to properly quote “et al.” in several citation styles:

In MLA style, “et al.” is used after the first author’s name on the paper’s reference page. For example, if a source has three or more authors, you would list the first author’s name followed by “et al.”, example:

Smith, John, et al. “The Effects of Climate Change on Biodiversity.” Environmental Science Journal, vol. 27, no. 2, 2020, pp. 25-34.

For in-text citations, you would include the first author’s name followed by “et al.” and at the end, the page number should be enclosed in parentheses, for example: 

(Smith et al. 36).

In the references page, put “et al.” after the first author’s name. If a source includes three or more authors, you would list the first author’s name followed by “et al.”, example:

Smith, J., Johnson, A., Williams, K., & Brown, M. (2019). “The Impact of Social Media on Adolescent Mental Health.” Journal of Adolescent Health, 65(3), 42-51.

In-text citations would include the first author’s name in parenthesis, followed by “et al.” and the year of publication, for example:

(Smith et al., 2019).

Chicago Format

On the reference page, “et al.” is used after the first author’s name in Chicago style. If a source includes four or more authors, you would list the first author’s name followed by “et al.”, for example:

Jones, S., et al. “The History of the American Civil War.” Civil War History, vol. 55, no. 2, 2009, pp. 34-47.

In-text citations would include the first author’s name in parenthesis, followed by “et al.” and the page number:

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Capstone Form and Style

Citations: using et al., using et al..

In APA 7, when citing a work with three or more authors, include the first author’s surname followed by “et al.” "Et al." is Latin for "and others." Do this every time you cite the source, including the first instance. For example, a parenthetical citation for a work by three authors (Rasmussen, Hopkins, and Fitzpatrick) with a publication date of 2004 would look like this:

In research-based development planning, decision-making is based on careful, systematic examination of goals, data, and results (Rasmussen et al., 2004).

A narrative citation would look like this:

Rasmussen et al. (2004) emphasized the vital role research plays in development planning, saying that thoughtful examination of data and evidence should be present.

Remember that there will not be a comma between the surname and “et al.,” and the period goes only after the “al.” The English translation of “et al.” is simply “and others.”

When citing a work by two authors, always include both authors’ names. Do not use “et al.”

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How to Use Et Al. in Every Format—Et Al. Meaning

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Written by  Scribendi

Have you ever come across "et al." and wondered what it meant? Or how to use it?

If so, you're not alone. This Latin phrase is commonly used in academic writing and can be confused with other Latin phrases like "etc."

Things get even more complex when you realize that the placement of et al. changes depending on what style guide you're using.

Read on for a simplified breakdown of how to use et al. in every format, so you never get stuck.

Et Al. Meaning

Before we get into the nitty-gritty details, it helps to first understand the literal definition of et al. That way, you'll know exactly what you're saying when you use the term.

The phrase "et al." is derived from the Latin phrase "et alia," which means "and others." You are likely to encounter et al. in the references, in-text citations, and reference lists of academic texts.

For example, you might see the phrase, "Horowitz et al. (2012) published groundbreaking research," which means that Horowitz and others published the research.

Why Is Et Al. Used?

Et al. is used to simplify citations within your text or reference list. It lets the reader know that other authors have contributed to the work you're citing, without you having to list every author.

Et al. is also used to simplify subsequent references to groups of coauthors that have already been cited in full. For example, if you're citing the same group over and over, using et al. can simplify that citation throughout your paper.

How to Write Et Al.

Where should i put the period.

The period in et al. should go at the end of "al" because "al" is an abbreviation for "alia," meaning "others."

There is no period after "et" because "et" isn't an abbreviation. It's a full word in Latin, meaning "and."

Remember, "et al." is the only correct way to type this phrase.

A trick for remembering to include the period after "al" is to think of another common abbreviation, "etc."

"Etc." abbreviates et cetera, meaning "and the rest," and it always requires a period at the end. So et al., which is similar, always takes a period at the end too.

Here are a few common misspellings of et al.:

When you use other punctuation with et al., like a comma, it goes after the period. But if you're ending a sentence with et al., you don't need an additional period.

Should I Italicize Et Al.?

Most major style guides (including APA, MLA, the Chicago Manual of Style, and Harvard) do not require et al. to be italicized. However, some field-specific publications do require the italicization of the phrase, so it's always a good idea to double-check.

Using et al. in a sentence appropriately varies among style guides. Check out the overviews of different style guides below to make sure you're using this tricky phrase correctly.

How to Use Et Al., with Examples

APA format, established by the American Psychological Association, is commonly used for publications, essays, reports, and books in the fields of psychology and social science.

Also called APA style, this format has established specific standards for scientific and scholarly writing. It encourages uniformity and consistency in the way content is organized and references are cited.

APA in-text citations, reference lists, and title pages adhere to formatting requirements that differ from those of other styles.

For example, APA includes the author's surname and publication year in in-text citations, using an ampersand if there are two authors:

(Smith, 2012)

(Smith & Jones, 2012)

Another differentiator between APA and other styles is that APA requires a cover page, called a Title Page, and uses the title "References" above the citation list at the end of papers or manuscripts.

Traditionally, APA format is used for a range of subjects in the social and behavioral sciences, including:

Linguistics

When to Use Et Al. in APA

When dealing with a work by three or more authors in APA format (seventh edition), use the first author's last name in the signal phrase or parenthesis, followed by et al.

(McKenzie et al., 2020)

McKenzie et al. (2020)

Keep in mind that et al. wouldn't be needed if you were citing just two authors. If you were citing two authors and you replaced one of their names with et al., meaning "and others," this would be incorrect.

Use et al. in APA in-text citations only if you're citing at least three authors, and remember that et al. is never used in the reference list in APA.

Et Al. Example in APA Format

The use of et al. in APA format differs from other styles when it comes to the References.

Its format requires listing the surnames and first initials of up to 20 authors, placing an ampersand before the final author.

Karloff, J., McMahon, S., Watson, C., Williamson, M., Russell, S., Holden, R., Williams, B., Messier, A., Nesbo, J., Lamott, A., Shaffer, M., Barrows, A., Perry, T., Rooney, K., Cruz, M., Warren, G., Granville, D., Gonzalez, R., Johnson, S., & Galloway, J.

For more than 20 authors, you would replace all authors after the 19th with ellipses, followed by the final author's name.

Karloff, J., McMahon, S., Watson, C., Williamson, M., Russell, S., Holden, R., Williams, B., Messier, A., Nesbo, J., Lamott, A., Shaffer, M., Barrows, A., Perry, T., Rooney, K., Cruz, M., Warren, G., Granville, D., Gonzalez, R., Johnson, S., … Galloway, J.

Et Al. in APA In-Text Citations with Multiple Authors

When citing three or more authors in text with APA (seventh edition), you can use et al. upon the first and subsequent references to a source.

Before the seventh edition of APA, the names of up to five authors had to be spelled out in the text. Et al. could only be used upon subsequent references.

Luckily, the seventh edition has been simplified. Here is an example of how to use et al. for in-text citations in APA.

Three or more authors:

Parenthetical: (Johnson et al., 2020)

Nonparenthetical: Johnson et al. (2020)

MLA format was developed by the Modern Language Association. It provides specific guidelines for students and researchers writing academically in the fields of language and literature.

Often called MLA style, this format allows for an easy reading experience. It offers a uniform and consistent method of adding citations to books or literature.

Using et al. in MLA is different from APA and other styles in its requirements for the use of et al. MLA has different standards for layout, citations, and abbreviations.

There are also slight differences in the way authors are cited. But the spelling of et al. is always the same, regardless of the style guide being used, with lowercase letters and no punctuation after "et"—the only punctuation is the period after "al."

MLA format is traditionally used by writers and students creating work in the following disciplines:

Language and literature

Comparative literature

Literary criticism

Cultural studies

If you're formatting an essay or paper in MLA, the most updated edition is the ninth, published in April 2021.

When to Use Et Al. in MLA

You can use et al. in MLA when referring to multiple authors—three or more, to be exact. And you can add et al. to both your in-text citations and your Works Cited page (the name for the reference list).

Et Al. Example in MLA Format

Let's look at how to cite multiple authors in MLA in your Works Cited page with et al.

See the following two examples for citing a collection of poems and a collection of stories using et al. in MLA.

O'Hara, Frank, et al. The Collected Poems of Frank O'Hara . University of California Press, 1995.

Levine, Robert S., et al. The Norton Anthology of American Literature . Ninth ed., W.W. Norton &

Company, 2022.

Note that the second line of the citation is indented by half an inch.

Et Al. in MLA In-Text Citations with Multiple Authors

Now, we'll review how to cite multiple authors using et al. in MLA in-text citations.

MLA format requires the inclusion of the first author's surname, then et al., and then the page number.

(Lackey et al. 56)

The above is an example of a parenthetical in-text citation with et al. Here is an example of how to incorporate it within your prose:

According to Gilbert et al., "Today, however, we can see more clearly just how complex and multifaceted Woolf's set of women writers really is" (23).

The Chicago Manual of Style, often called CMS, CMOS, or Chicago, is a style guide used by authors, editors, indexers, designers, and publishers to prepare manuscripts and to aid in the revision of grammar, punctuation, and usage.

Dubbed the "editor's bible," the Chicago Manual of Style is typically used with material intended for publication. It's the style most often applied to novels, blogs, and creative nonfiction.

A key differentiator of Chicago style is that it offers two systems for source citations: notes and bibliography or author-date.

The notes and bibliography system is used by scholars and writers working in the humanities, and the author-date system is preferred by writers in the fields of science and social science.

That being said, here are a few of the most common fields in which Chicago style is used:

Social science

Natural science

The most recent edition is the 17th, which was published in September 2017. Let's look at how to use et al. in Chicago style.

When to Use Et Al. in Chicago Style

In essays adhering to Chicago style, you can use et al. when citing a source with four or more authors.

The format and placement of et al. can vary because, as we mentioned earlier, Chicago uses two systems for source citation: notes and bibliography and author-date. So the placement really depends on which system you're using!

But as a general rule, you can use et al. in your in-text citations, in your footnotes and endnotes, and in your reference list at the end of your document.

Note that bibliographies go with the notes and bibliography system, and reference lists go with the author-date system.

Et Al. Example in Chicago Style

You will use et al. in bibliographic form in Chicago Style for sources with more than 10 authors. In such cases, you'll list the first seven authors, followed by et al.

The citation format in your bibliography will change depending on whether you're using the notes and bibliography system or the author-date system, but the placement and format of et al. are the same.

Notes and bibliography system:

Jackson, Tiffany D., Nic Stone, Ashley Woodfolk, Dhonielle Clayton, Angie Thomas, Nicola Yoon,

Natasha Schrader, et al. Blackout . New York, NY: Quill Tree Books, an imprint of

HarperCollins Publishers, 2021.

Author-date system:

Natasha Schrader, et al. 2021. Blackout . New York, NY: Quill Tree Books, an imprint of

HarperCollins Publishers.

Et Al. in Chicago Style In-Text Citations with Multiple Authors

When using et al. in an in-text citation of four or more authors, et al. can be formatted in a few different ways, depending on which source citation system you're using. Take a look at the examples below.

In the author-date system, et al. goes after the first author's surname in an in-text citation.

(Johnson et al. 2021, 465)

In the notes and bibliography system, et al. can go in a short or long footnote. Here's how the format breaks down for each type:

Short footnote: Johnson et al.

Long footnote: David Johnson et al.

Turabian style is similar to Chicago style when it comes to how to write et al. Published by Kate L. Turabian in 1937, this style was created for researchers and students. Its official title is A Manual for Writers of Research Papers, Theses, and Dissertations.

You can think of it as a student's version of Chicago style. Turabian style places greater emphasis on student needs regarding the formatting of papers and citations, and this is its biggest differentiator.

This manual is also shorter and contains fewer instructions than others. Another differentiator of Turabian is that it covers a wide spectrum of disciplines, including:

Art history

Social studies

Global studies

Religious studies

If you're looking for the latest edition, be sure to use the ninth, published in 2018.

When to Use Et Al. in Turabian Style

As in Chicago style, you can use et al. in a sentence in Turabian when citing four or more authors.

You can also use et al. when citing sources in both the main text and the bibliography, and this is true of both the notes and bibliography and the author-date citation systems.

Where you should put et al. and how you should format it will vary depending on which citation system you use. Just keep in mind that you can use et al. in Turabian style whenever you have four or more authors to cite.

Et Al. Example in Turabian Style

The great thing about using Turabian style is that if you understand how to use et al. in Chicago style, using it in Turabian will be a breeze.

Below are some examples of how to write et al. in either your bibliography (notes and bibliography system) or reference list (author-date system) in Turabian style.

Notes and bibliography system (book):

Using the Turabian citation system, you'll follow the same format for et al. Only the placement of the publication date changes. See the examples below.

Kitamura, Katie, Allen Johnson, Birk Meyer, Alex Fritas, Joan Bigsby, Becca Thomas, Greg 

Lewis, et al. A Separation . New York: Riverhead Books. 2017. 

Author-date citation system (book):

For more than 10 authors, list the first seven authors and follow them up with et al.

Kitamura, Katie, Allen Johnson, Birk Meyer, Alex Fritas, Joan Bigsby, Becca Thomas, Greg Lewis,       

et al. 2017. A Separation . New York: Riverhead Books. 

Et Al. in Turabian In-Text Citations with Multiple Authors

Using et al. in your in-text citations is the same in Turabian as it is in Chicago style. You'll put et al. in your footnotes (short and long) and within your text. Below are examples of each.

(Johnson et al. 2017, 45)

In the notes and bibliography system, et al. could go in a short or long footnote. Here's how the format breaks down for each type of footnote.

Short footnote: Weber et al.

Long footnote: Jesse N. Weber et al.

Harvard style is a popular formatting style across many universities. It's been known to go by a couple of different names, including the Harvard Referencing System and Author-Date Referencing.

There's no official connection between Harvard style and Harvard University. This style is simply another way for students to cite their sources and format their papers uniformly.

Common disciplines that use this style include the following:

Behavioral sciences

The thing to remember about Harvard style is that it isn't as cut-and-dried as other styles—different schools have different requirements. This means that using et al. in Harvard style can change depending on what school you go to.

Be sure to refer to your professor's instructions before using et al. in your papers.

For the purposes of this post, we'll be talking about how to use et al. following Harvard Business School's Citation Guide.

When to Use Et Al. in Harvard Style

While some aspects of Harvard style can vary across institutions, one thing everyone seems to agree on is that et al. should be used to cite four or more authors.

So you should use et al. when you're citing four or more authors in both your footnotes and in your bibliography. You can also use the term in both parenthetical statements and as a signal phrase.

Et Al. Example in Harvard Style

In the bibliography section of your paper, you can use et al. for academic citations of sources with four or more authors .

Unlike Chicago, you don't have to list a certain number of authors before you list et al.—you can simply use et al. after the first author's name.

Here are two examples, one for a book citation and one for a web citation:

Christensen, C. Roland, et al. Business Policy: Text and Cases . 5th ed. Homewood, IL: Richard 

D. Irwin, Inc., 1982.

Enright, Michael J., et al. "Daewoo and the Korean Chaebol." University of Hong Kong case no. 

HKU143 (University of Hong Kong, August 2001). Harvard Business Publishing. 

https://hbsp.harvard.edu/, accessed March 2007.

Et Al. in Harvard Style In-Text Citations with Multiple Authors

When it comes to using et al. in Harvard style in-text citations, you can use it in your footnotes, parenthetical phrases, and signal phrases.

See examples of each below.

³C. Roland Christensen et al., Business Policy: Text and Cases, 5th ed. (Homewood, IL:

Richard D. Irwin, Inc., 1982), p. 101.

Parenthetical phrase:

(Johnson et al. 2007)

Signal phrase:

Johnson et al. (2007)

Again, keep in mind that Harvard style gives your instructor leeway in their guidelines for how to format et al., so be sure to follow their instructions.

An additional way to cite references is to use Vancouver style. This style was developed in Vancouver in 1978 by medical journal editors. It is most commonly used in medicine and science.

The biggest difference between Vancouver and other styles is its use of numbers. Often called the Numbering System, Vancouver cites sources by placing numbers within parentheses or superscripts in the main text.

These citation numbers are tied to entries in your reference list. Like in other styles, your reference list in Vancouver style will have all of the sources you've cited within your text.

Some common fields that use Vancouver are as follows:

Biomedicine

As in Harvard style, keep in mind that some universities and organizations have their own specific formatting requirements when it comes to citing work with et al. in Vancouver style.

When to Use Et Al. in Vancouver Style

With Vancouver style, you can use et al. for both in-text citations and within the reference list.

You should use et al. in your reference list when citing more than six authors. If you're citing just six authors, you'll need to spell out each author's surname and first initial, separating each author with a comma.

You should use et al. within the main text when citing multiple authors. Some universities differ in terms of how many authors, so it's best to check with your institution to confirm its preferences for this style.

Et Al. Example in Vancouver Style

Let's start our et al. examples for Vancouver with those in bibliographic form.

In Vancouver style, the bibliography is called a reference list. You'll add et al. to reference entries only if you're listing more than six authors. List the first six authors, then add et al.

Here's an example of a book citation with et al. in the reference list:

Doornbos MM, Groenhout ER, Hotz GK, Brandsen C, Cusveller B, Flikkema M, et al. 

Transforming care: a Christian vision of nursing practice. Grand Rapids, Michigan: 

William B. Eerdmans Publishing Company; 2005.

Note that the authors' surnames are followed by their first and (in many cases) middle initials, without punctuation.

Here's an example for an electronic journal article:

Aho M, Irshad B, Ackerman SJ, Lewis M, Leddy R, Pope T, et al. Correlation of sonographic

features of invasive ductal mammary carcinoma with age, tumor grade, and 

hormone-receptor status. J Clin Ultrasound [Internet]. 2013 Jan [cited 2015 Apr 

27];41(1):10-7. Available from: https://onlinelibrary.wiley.com/doi/10.1002/jcu.21990/full 

DOI: 10.1002/jcu.21990

Et Al. in Vancouver Style In-Text Citations with Multiple Authors

As far as in-text citations go in Vancouver style, you can use et al. directly in the text, followed by a reference number.

Because Vancouver references sources within parentheses or superscripts, here are examples using et al. in-text with both systems:

Harrison et al. (5) agree that only one solution is viable.

Harrison et al. 5 agree that only one solution is viable.

Et Alibi, Et Alii, and Others

Sometimes, et al. can be confused with other Latin phrases like et alibi and et alii. This is understandable because the terms all begin with the same letters!

Don't worry. Over the next few sections, we'll break down what each of these phrases means. That way, if you need to use them in your next paper or article, you won't use them incorrectly.

Et alia is the Latin phrase for "and others," and the phrase "et al." is its abbreviated form.

Et alia is meant to be used when a list contains too many people or things to name. In academic writing, it is used when citing sources with multiple authors.

However, the full phrase "et alia" isn't typically spelled out in academic writing. In papers, journals, and manuscripts, the abbreviated form "et al." is used, with a period after "al."

Et alibi means "and elsewhere" in Latin. It's used in academic writing to show that the information you're citing is mentioned in other parts of a text, too.

For example, if you're citing a passage from the Bible that can also be found in other locations of the text, that would be a perfect instance for using et alibi.

Keep in mind that "et al." is the abbreviated form of both et alibi and et alia.

Et aliae also means "and others" but in the feminine plural form. This means that et aliae refers specifically to a group of women or girls.

However, you won't need to differentiate between feminine or masculine forms when using et al. in your writing. You would simply use "et al."—the abbreviated form of both.

The Latin phrase et alii means "and others" in the masculine plural form. It’s used to refer to a group of men or boys.

But the abbreviated form, "et al.," is still what you would use to cite multiple authors.

As long as you can remember how to write the abbreviation et al. in your papers, you're good to go!

Difference between Et Al. and Etc.

Do you ever confuse et al. with etc.? You're not alone. The two are very similar.

While et al. means "and others" in Latin, etc. is short for the Latin et cetera and means "and the rest."

Both phrases indicate that something has been omitted from the text, and both are abbreviations. However, there are key differences to keep in mind to avoid using them incorrectly in your paper.

You use etc. to shorten a list. Its use lets the reader know that there are more items or examples you could list but that the shortened list allows the reader to get the idea.

For example, if you were to write, "The event is at the beach, so bring your swimsuits, towels, sunscreen, sandals, etc.," readers know they need to bring all beach items, not just the ones mentioned.

Similarly, you use et al. to shorten a list of authors or collaborators.

Common Mistakes

Spelling and formatting Latin phrases is no walk in the park—especially when you need to get them right to earn a passing grade.

It also doesn't help that each style guide has its own formatting or that many Latin phrases can sound the same. It's enough to make your head spin!

Below, we'll cover common mistakes made when using et al. and why using it is so important for clear and concise academic writing.

Spelling Latin phrases can be tricky, but abbreviating them correctly can be even trickier.

When using et al. in your papers, be sure to abbreviate it correctly and to use the right punctuation.

Et al. is always spelled as two separate words—"et" and "al"—with a period after "al."

The best way to remember how to punctuate and spell it is to remember that it's an abbreviation.

Here are a few common misspellings of et al. so you know to avoid them:

Using the Incorrect Style

Spelling et al. correctly is only half the battle. You'll also need to be sure you're using et al. in the style required by your university, institution, or professor.

As we mentioned earlier, there are many style guides to choose from, including MLA, Chicago, APA, and Turabian.

Each style has its own specific format for et al., so be sure to study its guidelines carefully before adding et al. to your references.

You'll especially want to take note of how et al. is used in both in-text and reference list citations and how many authors necessitate its use.

Not Using Et Al.

Using et al. is a clear and concise way of communicating your source information to readers without overwhelming them or taking away from your work.

It lets readers know that multiple authors or collaborators contributed to the source without having to list them all. Also, when referencing a source with several authors or collaborators multiple times, the use of et al. keeps the writing neat and tidy.

Not using et al. would make academic writing awkwardly long and arduous within the main text while extending bibliographies and reference lists unnecessarily.

Et al. helps academic writers and authors reference their sources in a clean-cut way.

How to Cite a Tweet

Nowadays, it's not uncommon for students or researchers to turn to social platforms like Twitter for their research.

Because of this, styles like MLA, APA, and Chicago have stayed current by offering standards for formatting citations of Tweets in research papers and scholarly articles.

Each style has its own formatting requirements for citing a Tweet, and these can vary among different editions of the same style.

Below are instructions for citing Tweets in each of the three major styles.

To cite a Tweet in MLA (ninth edition), you'll cite the first name and surname of the account holder (or the name of the organization) in addition to the Twitter handle.

Here is the basic structure:

Surname, First name [Username]. "Tweet message." Twitter , date posted, URL.

Here's an example:

Swift, Taylor [@taylorswift13]. "I'm so proud of this song and the memories I have with you guys 

because of it." Twitter , 22 November 2021, 

twitter.com/taylorswift13/status/1462908809542787072.

To cite a Tweet from an organization in MLA, you'll use this structure:

Organization or Account Name [Username]. "Tweet message". Twitter , date posted, URL.

The Wall Street Journal [@WSJ]. "Activist hedge fund Trian has acquired a stake in Unilever, 

people familiar with the matter say, adding pressure on the consumer-goods company." 

Twitter , 23 January 2022, twitter.com/WSJ/status/1485356694972551171.

To cite a Tweet in APA style (seventh edition), you'll do things a little differently from MLA. APA requires only the author's full surname with the first name initialized.

You'll also include only the first 20 words of the Tweet in your reference.

Surname, Initials [@username]. (Year, Month Day). Text of Tweet [Tweet]. Twitter. URL

Gates, B. [@BillGates]. (2019, September 7). Today, it's difficult for researchers to diagnose 

#Alzheimers patients early enough to intervene. A reliable, easy and accurate diagnostic 

would [Thumbnail with link attached] [Tweet]. Twitter.  

https://twitter.com/BillGates/status/1170305718425137152

To cite a Tweet in Chicago style, you'll include many of the same elements as Tweet citations in other styles, but you'll also add a timestamp.

The general structure is as follows:

First name Surname (@TwitterHandle), "Text of Tweet," Twitter, Month Day, Year, 00:00 

a.m., link to Tweet.

Here's an example from the Chicago Manual of Style:

Conan O'Brien (@ConanOBrien), "In honor of Earth Day, I'm recycling my Tweets," Twitter, April 

22, 2015, 11:10 a.m., https://twitter.com/ConanOBrien/status/590940792967016448.

If you'd like to cite a Tweet within your text, here's an example using the above Tweet:

Conan O'Brien's Tweet was characteristically deadpan: "In honor of Earth Day, I'm recycling my Tweets" (@ConanOBrien, April 22, 2015).

Frequently Asked Questions

What does et al. mean in a citation.

In a citation, et al. indicates that multiple authors are being cited within a reference in an academic work but that not all of their names are listed.

It's not uncommon for some sources to have 10 or even 20 authors, given the collaborative nature of research in the fields of medicine and science. Using et al. is a way of ensuring that all authors are referenced without crowding the content.

When Should Et Al. Be Used in APA Style?

Use et al. in APA in-text citations with multiple authors, as well as in the References. Specifically, use it when dealing with a work by three to five authors. You'll use the first author's surname in the signal phrase, parenthetical statement, or bibliographic entry, followed by et al.

Keep in mind that you should use et al. only for three or more authors, not two. Since et al. is an abbreviation for "and others," it must stand in for more than one person. If you were trying to cite two authors and you used et al. after the first one, et al. would represent one person as opposed to several "others," which would be incorrect.

What Is Et Al. in MLA?

In MLA style, et al. is an abbreviated Latin phrase meaning "and others." It indicates that multiple authors contributed to the source being cited but that not all of them are listed.

MLA recommends using et al. for sources with three or more authors. Et al. can be used both within the main text and on the Works Cited page. It's punctuated in the same way as in other styles, with a period after "al" only.

Here is a citation example using et al. in MLA:

(Gubar et al. 56)

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Using “et al.” in in-text reference citations in research papers

When writing research papers , most researchers would have come across the term “et al.” This is the abbreviation for a Latin phrase—written variously as et alii (masculine), et aliae (feminine), and et alia (neuter)—which means “and others.” The term “et al.” is mainly used for in-text citations of research papers having multiple authors, although some style guidelines also advocate the use of “et al.” in the reference list.

Ethical publication emphasizes that authors should provide an inclusive list of their sources in their manuscripts. This is because citations give credibility to a research work and help avoid plagiarism by crediting the original research work on which the present work is based. However, different journals and organizations follow different reference citation styles, which make it difficult to generalize the use of “et al.” when citing references.

Given below are a few citation style guidelines that outline the use of “et al.”

American Psychological Association (APA) Style Guide (6 th edition): For references having three to five authors, APA states that all the author surnames (last names) should be cited at the first instance, and citations thereafter should include the first author’s surname followed by “et al.” But for research papers with six or more authors, the surname of the first author is always cited followed by “et al.” Note that “et al.” should not be in italics, and “al” should be followed by a period.

Example: Three to five authors, (Kernis, Cornell, Sun, Berry, & Hallow, 1993) or Kernis, Cornell, Sun, Berry, & Hallow (1993) will be used as the first citation, and (Kernis et al., 1993) or Kernis et al., (1993) should be used in subsequent citations.

Six or more authors: (Harris et al., 2001) or Harris et al. (2001)

Modern Language Association (MLA) Style Manual: For research papers having three or more authors, MLA states that, for the reference list, the first author’s surname should be cited, followed by a comma, then the rest of the name, followed by “et al.” For in-text citations, the first author’s surname is followed by “et al.”

Example: Russell, Tony, et al. (2016) for reference list; Russell et al. (2016) for in-text citation.

Chicago Manual of Style (CMS): For four to ten authors, write out all names in the bibliography but only the first author’s name followed by “et al.” in in-text citations.   For more than ten authors, only the first seven are listed in the bibliography, but the first author’s name followed by “et al.” is used in in-text citations. Note that “et al.” is not italicized.

Example: Acoose et al. (2008) or (Acoose et al., 2008) for in-text citation.

As previously mentioned, different style guidelines have adopted different rules for using “et al.” So, the best way to use “et al.” is to check the guidelines of your target journal or organization and follow the style accordingly.

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Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

In-Text Citations: Author/Authors

Welcome to the Purdue OWL

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Though the APA's author-date system for citations is fairly straightforward, author categories can vary significantly from the standard "one author, one source" configuration. There are also additional rules for citing authors of indirect sources, electronic sources, and sources without page numbers.

A Work by One Author 

The APA manual recommends the use of the author-date citation structure for in-text citation references. This structure requires that any in-text citation (i.e., within the body of the text) be accompanied by a corresponding reference list entry. In the in-text citation provide the surname of the author but do not include suffixes such as "Jr.". 

Citing Non-Standard Author Categories

A work by two authors.

Name both authors in the signal phrase or in parentheses each time you cite the work. Use the word "and" between the authors' names within the text and use the ampersand in parentheses.

A Work by Three or More Authors

List only the first author’s name followed by “et al.” in every citation, even the first, unless doing so would create ambiguity between different sources.

In  et al. , et  should not be followed by a period. Only "al" should be followed by a period.

If you’re citing multiple works with similar groups of authors, and the shortened “et al” citation form of each source would be the same, you’ll need to avoid ambiguity by writing out more names. If you cited works with these authors:

They would be cited in-text as follows to avoid ambiguity:

Since et al. is plural, it should always be a substitute for more than one name. In the case that et al. would stand in for just one author, write the author’s name instead.

Unknown Author

If the work does not have an author, cite the source by its title in the signal phrase or use the first word or two in the parentheses. Titles of books and reports are italicized; titles of articles, chapters, and web pages are in quotation marks. APA style calls for capitalizing important words in titles when they are written in the text (but not when they are written in reference lists).

Note : In the rare case that "Anonymous" is used for the author, treat it as the author's name (Anonymous, 2001). In the reference list, use the name Anonymous as the author.

Organization as an Author

If the author is an organization or a government agency, mention the organization in the signal phrase or in the parenthetical citation the first time you cite the source, just as you would an individual person.

If the organization has a well-known abbreviation, you may include the abbreviation in brackets the first time the source is cited and then use only the abbreviation in later citations. However, if you cite work from multiple organizations whose abbreviations are the same, do not use abbreviations (to avoid ambiguity).

Two or More Works in the Same Parentheses

When your parenthetical citation includes two or more works, order them the same way they appear in the reference list (viz., alphabetically), separated by a semi-colon.

If you cite multiple works by the same author in the same parenthetical citation, give the author’s name only once and follow with dates. No date citations go first, then years, then in-press citations.

Authors with the Same Last Name

To prevent confusion, use first initials with the last names.

Two or More Works by the Same Author in the Same Year

If you have two sources by the same author in the same year, use lower-case letters (a, b, c) with the year to order the entries in the reference list. Use the lower-case letters with the year in the in-text citation.

Introductions, Prefaces, Forewords, and Afterwords

When citing an Introduction, Preface, Foreword, or Afterword in-text, cite the appropriate author and year as usual.

Personal Communication

For interviews, letters, e-mails, and other person-to-person communication, cite the communicator's name, the fact that it was personal communication, and the date of the communication. Do not include personal communication in the reference list.

If using a footnote to reference personal communication, handle citations the same way.

Traditional Knowledge of Indigenous Peoples

When citing information you learned from a conversation with an Indigenous person who was not your research participant, use a variation of the personal communication citation above. Include the person’s full name, nation or Indigenous group, location, and any other relevant details before the “personal communication, date” part of the citation.

Citing Indirect Sources

Generally, writers should endeavor to read primary sources (original sources) and cite those rather than secondary sources (works that report on original sources). Sometimes, however, this is impossible. If you use a source that was cited in another source, name the original source in your signal phrase. List the secondary source in your reference list and include the secondary source in the parentheses. If you know the year of the original source, include it in the citation.

Electronic Sources

If possible, cite an electronic document the same as any other document by using the author-date style.

Unknown Author and Unknown Date

If no author or date is given, use the title in your signal phrase or the first word or two of the title in the parentheses and use the abbreviation "n.d." (for "no date").

Sources Without Page Numbers

When an electronic source lacks page numbers, you should try to include information that will help readers find the passage being cited. Use the heading or section name, an abbreviated heading or section name, a paragraph number (para. 1), or a combination of these.

Note:  Never use the page numbers of webpages you print out; different computers print webpages with different pagination. Do not use Kindle location numbers; instead, use the page number (available in many Kindle books) or the method above. 

Other Sources

The  APA Publication Manual  describes how to cite many different kinds of authors and content creators. However, you may occasionally encounter a source or author category that the manual does not describe, making the best way to proceed unclear.

In these cases, it's typically acceptable to apply the general principles of APA citation to the new kind of source in a way that's consistent and sensible. A good way to do this is to simply use the standard APA directions for a type of source that resembles the source you want to cite. For example, a sensible way to cite a virtual reality program would be to mimic the APA's guidelines for computer software.

You may also want to investigate whether a third-party organization has provided directions for how to cite this kind of source.

Et tu, Et al.? How to Cite Multiple Authors in Academic Writing

You’ve done your research, you’ve made your bibliography, and you’re ready to write. But after a short time, you find yourself stuck. In-text citations are driving you crazy! Do you really have to list all six authors of the paper you are referencing? What if the first two authors are the same on two different papers? Is it the same regardless of citation style? Read on to remove your confusion about multiple authors in-text citations.

Single Author In-text Citations: A Refresher

There are three major styles of citation : APA, MLA, and Chicago/Turabian. APA is used most often by Education, Psychology, and Sciences,  MLA is favored by the Humanities, and Chicago by Business, History, and Fine Arts. As the guidelines for author in-text citations vary slightly among the three, it is important to know the difference.

APA requires two types of information: the author’s last name and the date of publication of the work you are citing. If you are citing a direct quote, you must also add the page number.

There was no direct causal relationship found between the two events (Burnett, 1995)

Burnett (1995) noted that “Subsequent investigation revealed that the two events had no direct causal relationship to one another,” (p.147).

MLA style requires only the author and page number, as seen in the example below. There is no difference in citation style between a direct quote or a paraphrase.

It is still unknown whether caffeine delays the onset of Alzheimer’s disease (Grant, 204).

Chicago style requires all three whether you are paraphrasing or not.

A daily serving of broccoli was found to help patients recover more quickly from scurvy (Poblanski 2015, 99-100).

Citing Multiple Authors: How should you use “et al.”?

“Et al.” is a Latin term that means “and others,” and is used for in-text citations of works with multiple authors. The guidelines for using “et al.” vary slightly among the three major formatting styles.

MLA uses “et al.” for works with three or more authors, while Chicago calls for using it with four or more authors. APA format requires that you cite all of the authors at the first mention if there are three, four, or five , and use “et al.” afterward. If there are at least six authors, then you may use “et al.” from the first mention. In all cases, you should use the last name of the first author followed by “et al.” in your in-text citation.

For a paper written by Henderson, Watts, and Kirkland, the MLA citation would look like this:

Peanut butter is a rich source of protein (Henderson, et al. 328).

According to Henderson et al., peanut butter is a rich source of protein (328).

For a paper written by Rhyu, Lee, McSnyder, and Xi, the Chicago citation would look like this:

• Japanese wartime aggression remains a controversial topic in much of East Asia (Rhyu et al. 2012, 45).

According to Rhyu et al. (2012), Japanese wartime aggression remains a controversial topic in much of East Asia (45).

For the same paper cited in APA format, the first citation would be as follows:

• Japanese wartime aggression remains a controversial topic in much of East Asia (Rhyu, Lee, McSnyder, and Xi, 2012).

Additional in-text citations of the same paper in APA format would look like this:

South Korea’s state history textbook controversy of 2014 is a good example of this debate (Rhyu et al. 2012).

Same Authors, Same Year, Different Article

“Et al.” can create ambiguity in some situations. Take the following example of two publications.

• Lee, J. N., Lebowski, B., Kelly, J., & Ryan, T. (2000). “Intellectual Property Law in FTA Negotiations.” Journal of East Asian Affairs, 13, 14–25.
• Lee, J. N., Lebowski, B., Kelly, J., & Ryan, T. (2000). “Multinational Corporate Influence in the WTO.” Journal of World Trade, 67, 38-55.

Each citation style solves this problem a little differently. MLA adds the name of the text in parentheses, while APA and Chicago recommend adding a letter after the year to distinguish between the works.

MLA : Lee et al. point out that FTA negotiations have gone far beyond the original scope of goods and services trade to incorporate regulatory measures (“Intellectual Property Law in FTA Negotiations,” 20).

APA/Chicago : Lee et al. (2000a) point out that FTA negotiations have gone far beyond the original scope of goods and services trade to incorporate regulatory measures.

Note that in the bibliography of your paper, if you are using APA or Chicago style and you distinguish two papers this way, your bibliography should reflect this. For example:

• Lee, J. N., Lebowski, B., Kelly, J., & Ryan, T. (2000a). “Intellectual Property Law in FTA Negotiations.” Journal of East Asian Affairs, 13, 14–25.
• Lee, J. N., Lebowski, B., Kelly, J., & Ryan, T. (2000b). “Multinational Corporate Influence in the WTO.” Journal of World Trade, 67, 38-55.

Et al. is Always Plural

One last thing to note about “et al.” is that it is plural: it can never refer to only one author. What should we do in the following situation? We are citing the following two papers in APA format.

• Lee, J. N., Lebowski, B., Kelly, J., Ryan, T, & Grant, R. (2000). Pharmaceutical Access and Intellectual Property Law in the WTO. Pacific Review, 15, 177–209.

The first in-text citation of these two papers would be as follows.

• (Lee, Lebowski, & Ryan, 2000)
• (Lee, Lebowski, Ryan, & Grant, 2000)

However, if we write (Lee et al., 2000), we are left with two identical citations. We cannot use (Lee, Lebowski, & Ryan et al. 2000), because “et al.” should refer to two more people. So, we must write all four names each time we cite it.

How do you make sure to use et al. correctly? What else confuses you about citations? Let us know in the comments!

I just want to use forum to thank Enago academy for delivering this resource material to us free of charge. I have this question also and that is ‘when an author is citing another author in an in-text citing who was cited by an author in a text, what is the new standard for this citation in APA?’ Emengini steve Emeka

Dear Emeka Emengini,

Thank you for getting in touch with Enago Academy. The following APA blog post nicely addresses your original query: http://blog.apastyle.org/apastyle/2010/05/secondary-sources-aka-how-to-cite-a-source-you-found-in-another-source.html

It is generally a good idea to cite the original source. Secondary sources may be cited only under certain circumstances, as outlined in the above APA blog post. Enago Academy had posted a related article on the APA style guide earlier this year. In case you have more questions for us, please route them through the Q&A Forum. It’s a FREE service for authors. Make sure you share this with your colleagues too. Have a wonderful week ahead and season’s greetings!

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Home / Guides / Citation Guides / MLA Format / How to use et al. in MLA

How to use et al. in MLA

When you need to cite sources that have three or more authors or contributors, you don’t have to cite all of the contributors’ names. Instead, you can use et al.

Et al. is an abbreviation for the Latin word, et alii, which means “and others.” Using et al. shows that three or more contributors wrote, edited, or collaborated on the work, even though only one name is listed in the citation.

Using et al. in MLA

There are many places in mla citation style where you can use et al..

• Works with three or more writers
• Works with three or more editors
• Collections of essays, stories, or poems with three or more contributors

Citing a journal article in MLA is a common instance where you may need to use et al., as journal articles often have three or more authors.

When to use et al.

You can use et al. in both your MLA in-text citations and the Works Cited page. When using et al., you should always use the name of the writer listed first in the source material.

Note: Using et al. should not be confused with etc. or other abbreviations that indicate more content than listed. For example, etc. is an abbreviation for et cetera and is used at the end of a list to indicate that there are other similar items included in the list that are not names.

How to Format et al. in MLA Style

The format to write et al. is always the same: et al. Use lowercase letters with no punctuation after et and a period after al.

To format an in-text citation

• Use the first writer’s last name. Use the first writer listed on the source material. Do not use any of the other writers’ names.
• Follow the last name with et al. Write et al. in lowercase letters. There is no punctuation after the et, and there is always a period after the al.
• Other end punctuation can come after the period following al., but you must include the period because this is an abbreviation.

Example et al. citations for the following source

• Title: “Interrogating Disciplines/Disciplinarity in WAC/WID: An Institutional Study”
• Author(s): Anne Ruggles Gere, Sarah C. Swofford, Naomi Silver and Melody Pugh.
• Source: College Composition and Communication , vol. 67, no. 2, 2015, pp. 243–266

In-text citation example

(Gere et al. 243)

The Works Cited page citation for that source

Gere, Anne Ruggles, et al. “Interrogating Disciplines/Disciplinarity in WAC/WID: An Institutional Study.”  College Composition and Communication , vol. 67, no. 2, 2015, pp. 243–266. JSTOR , www.jstor.org/stable/24633857.

NOTE: A comma is needed after the name before et al. in the works cited citation, but it is not required for the in-text citation example.

Works cited

Gere, Anne Ruggles, et al. “Interrogating Disciplines/Disciplinarity in WAC/WID: An Institutional Study.”  College Composition and Communication , vol. 67, no. 2, 2015, pp. 243–266., www.jstor.org/stable/24633857. Accessed 6 Oct. 2020.

MLA Handbook . 9th ed., Modern Language Association of America, 2021.

Published October 25, 2020.

By Catherine Sigler. Catherine has a Ph.D. in English Education and has taught college-level writing for 15 years.

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What does ‘et al.’ mean and How to Use ‘et al.’ in a Research Paper

A majority of researchers wonder how to use et al. in a research paper. Et al. is one of the most commonly used Latin abbreviations, just like as,  etc. ,  versus ,  circa ,  ibid.  and  id. , and often crops up in academic writing. While the English phrases of all these above mentioned words are acceptable, researchers use Latin abbreviations as they take less time and fewer characters to write. Yet it’s not always easy to get these right.

In this article, we focus on one such abbreviation – et al. by explaining what does et al. mean and how to use et al. in a research paper correctly

Table of Contents

Et al. definition: what does et al. mean in academic writing, how to use et al. in a research paper, how to use et al. in a research paper: common mistakes to avoid.

The number of co-authors in an academic publication is, in principle, unlimited. Imagine having to write the names of all the authors in your bibliography. This is where et al. comes into play to indicate other authors in an academic work.

Et al. is the abbreviated form of et alia (or et alii or et aliae, the masculine and feminine plural, respectively). According to the Cambridge Dictionary, 1 the synonyms for et al. are “also,” “extra,” and “in addition.” Et al. is mostly used to indicate more than two people; it can also simplify subsequent references to groups of co-authors already cited in full. For example, when citing the same group of authors multiple times in your paper, using et al. can simplify the citations.

The number of authors to be listed before et al. can vary depending on the style guides. A few guidelines on the proper use of et al. in citations and references are given below. 2

• APA Style Guide
• Reference list : Et al. is never used in the reference list in APA.
• In-text Citation : Use et al. only if citing at least three authors (seventh edition). Use the first author’s last name in the signal phrase or parenthesis, followed by et al. For example,

Parenthetical: (Smith et al., 2020)

Nonparenthetical: Smith et al. (2020)

• MLA Style Guide
• Reference list : Use et al. when referencing work with three or more authors; include only the first author, followed by a comma, and the words et al, ending with a period.
• In-text Citation : Use et al. when citing a work with three or more authors. The author name is followed by the page number in place of the year. For example,

Parenthetical: …(James et al. 157-65).

Nonparenthetical: James et al. (157-65)

• Chicago Style Guide
• Reference list : When a source has more than 10 authors, list the first seven followed by “et al.” Otherwise, list every author.
• In-text Citation : When a source has four or more authors, give only the first author’s name followed by “et al.” For example,

(Bay et al. 2017, 465)

• Vancouver Style Guide
• Reference list : When a source has more than six authors, list the first six followed by “et al.” Otherwise, list every author.
• In-text Citation : When a source has three or more authors, give only the first author’s name followed by “et al.” Use et al. directly in the text, followed by the reference number. For example,

Doornbos et al. (5) agree that only one solution is viable.

• Plural vs. singular: Wondering if et al. is a plural or singular verb? Whenever this confuses you, remember that because a phrase ending in “et al.” refers to a group of people, you will use plural verbs when the “et al.” phrase is the subject.

Incorrect: Smith et al. (2015) states that …

Correct: Smith et al. (2015) state that …

Also, “et al.” is plural and indicates at least two people. So, you cannot use et al. to substitute for only one author. For example, if you are dealing with three authors and have typed out two names, the last author cannot be replaced with et al.

• Punctuation: “Et al.” is commonly misspelled as “et all,” “et. al.,” “et. al,” or “et-al.” Remember, “et al.” is composed of two words, with the “al” always followed by a period. The period indicates that the term is an abbreviation.
• Using the incorrect style: Decide on the style guide to follow before you start your writing. The use of et al. in a sentence can vary if using APA, MLA, etc.
• Possessive noun: When using a possessive noun, use “ ’s ” after “et al.”

Correct: In Smith et al.s’ study.

Correct: In Smith et al.’s study.

But, it’s best to avoid possessive phrasing when using et al. Instead, change it “Smith et al. (2015) found that . . .” or “In a study by Smith et al.”

• Italics: Italicizing is unnecessary when using “et al.” But this is more of a style guideline and can vary.
• “Et Al.” vs. “Etc.” and “Et Alibi”: “Et al.,” is sometimes confused with “Etc.” and “et alibi” but they mean different things and have other usages. “Etc.” meaning “rest,” is used at the end when listing things rather than people. “Et Alibi” means “and elsewhere” and is used when listing places or locations.

Finally, remember that when you think of the meaning of et al. in research, it is a word used to indicate other authors in the list. It is not intended to highlight the first author’s contribution as more important than the others, but simply to save space and time.

• Cambridge Dictionary https://dictionary.cambridge.org/dictionary/english/et-al
• Purdue Online Writing Lab. APA Formatting and Style Guide (7 th edition) https://owl.purdue.edu/owl/research_and_citation/apa_style/apa_formatting_and_style_guide/general_format.html

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Use of et al. – for referencing in an academic paper

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“Et al.” is a popular expression used by college and university students when citing a research source having more than one author. Included in this article is its definition, how to use it when using different citation styles, and the most frequently asked questions regarding the use of et al. The information contained here is vital, as it will assist you to know how to use the term correctly, which may, in the long run, help in boosting your grades.

Inhaltsverzeichnis

• 1 Use of et al. - FAQ
• 2 Use of et al.: Definition
• 3 Use of et al. in Citation
• 4 Use of et al. Common Mistakes
• 5 In a Nutshell

Use of et al. - FAQ

When do you need to use et al..

Et al. is an abbreviation of et al. ii, a Latin expression, which means ‘and others’. You often need to make use of et al. in a citation that has three or more authors. Its purpose is to assist in making the citations manageable. If you are using the author’s name, you have to ensure you add a full stop after writing et al.

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How do you punctuate et al.?

Some college students don’t know how to make the right use of et al. Whenever you have to use the term, you have to note that the “al” should always have a period after it. The period is vital because et al. is an abbreviation . Including the period helps to show this to the reader.

How do you read et al.?

Learning the use of et al. also means learning how to pronounce it. If reading it aloud, you will be required to pronounce the term in full, i.e., “et alia” or “et al. ii”. On the other hand, you could also choose to say “and others.” It’s the same way you would opt to say “for example,” as opposed to reading the abbreviation “e.g.”

Can you start an email with et al.?

Not sure how to make use of et al. in an email? It’s possible to do so. For example, in the greeting section, you could say Dear Daniel et al., Hello, Kevin et al., Remember that the expression stands for “and others.”

Should et al. be Italicized?

When using et al., you shouldn’t underline or italicize it. You have to write it without either of the two. As a rule, the most commonly used Latin abbreviations and words shouldn’t be italicized.

Use of et al.: Definition

Definition 1: et al. and others: It’s an abbreviation of ‘et alii’ which is used when the author is referring to a group of people. Definition 2: et al. and elsewhere: Authors use it when they want to refer to other occurrences in the text. Why it’s used: When citing papers that use the name and dating system, it can prove awkward when the author provides a long string containing numerous names. It’s the reason why many scientific journals recommend that authors make use of et al. When it’s used: Its recommended to try to make use of et al. when an author doesn’t want to have to name all the things or people in a list. The abbreviation works in the same manner as “etc.”

Use of et al. in Citation

Using Et Al. in APA Citation

APA citation happens to have a few quirks, with one of them being in the use of et al. While the abbreviation is used when citing sources having many authors, the 7th APA citation edition happens to differ from the rest in terms of how to make use of et al.

Only make use of et al. when using in-text citations

The 7th edition states that et al. should only be used when one is using in-text citations. It’s a significant change from the previous edition where authors could use et al. in the reference list. This means that the reference list in the 7th edition doesn’t support the use of et al.

In-text citation format using et al.

Et al. should only be used in in-text citations when an author wants to reference a source having three or more authors. Here, you can make use of et al. by including the authors first name, and then including et al. in every other Citation.

Exceptions: Multiple works sharing a single author

There are instances when making use of et al. could lead to unwanted problems. For example, when numerous works share the same three authors and year of publication, simply writing “et al.” could muddy the waters. When dealing with such a case, it’s recommended to write as many names as possible to help differentiate the references. You can then make use of et al. for any remaining names.

Using Et Al. in MLA Citation

For MLA citation , it’s recommended that you make use of et al. whenever there are sources with more than three sources. It’s a rule that applies to both the Works Cited list and the in-text citations.

Using Et Al. in Chicago Citation

Chicago Style Citation traditionally has two citation systems: author-date style and notes and bibliography style. The use of et al. doesn’t differ in both styles. When working with sources with one, two, or three plus authors, you will need to list all their names in your in-text citations (author-date or footnotes).

In case you have a source with four-plus authors, then it’s advisable to use et al. by listing the first name and following it up with et al. In the Chicago style bibliography or reference list, you will need to list up to ten authors. For any source with over ten authors, you should list the first seven and then follow this with et al.

For example, Harold Peters, McDonnel, Anne Elliot, Frederick, Robert Davis, Molly Davidson, Ronald Clobus, Jessica Singh, et al.

Use of et al. Common Mistakes

I. Most students tend to make use of et al. with works that don’t have multiple sources. Remember, you only need to use it when the source has more than three authors. II. Punctuation Mistakes: the “al” in “et al.” should always have a period after it. The reason for using the period is because “et al.” is an abbreviation. It’s why you need the period.

• Where necessary, it can also be followed by another punctuation mark where deemed necessary. However, make sure that the period comes first, before the other punctuation mark.

III. Et al. vs etc. Some students end up confusing “etc.” with et al. This shouldn’t happen as “etc.” is used for concepts and lists of things whereas “et al.” is primarily used when dealing with lists of people.

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In a Nutshell

• Et al. is an abbreviation for a Latin term “et alia” which means “and others.”
• The expression is commonly used in academic papers when a writer wants to cite more than one author
• Each citation style has its own rules on how to use et al. in both the in-text citations and in the works cited section.
•  Common FAQs on making use of et al. have to do with reading it aloud and punctuating it correctly.

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Significance and implications of accurate and proper citations in clinical research studies

Citations are an essential component of clinical research studies. In health sciences most articles will refer to over 20 other peer-reviewed publications [ 1 ]. Citations are a core part of the entire research process. Citations fuel literature reviews [ 2 , 3 ] and they allow researchers to link their experiments to previous results and conclusions and establish credibility [ 2 , 4 , 5 ]. Citations can help authors contribute to the growing compilation of literature and prevent plagiarism [ 6 , 7 ]. However, prior studies have acknowledged a prevalence of improper citation [ [8] , [9] , [10] , [11] ]. Studies report citation inaccuracy rates of approximately 20–26% in biomedical literature [ 8 , 9 ]. Some studies have also reported citation inaccuracies within field-specific journals such as pediatric orthopaedics [ 8 ], neurosurgery [ 12 ], spine surgery [ 13 ], and foot and ankle surgery [ 14 ]. This trend is especially alarming as citation inaccuracies can diminish research validity [ 15 ]. Recognizing the causes or instances of inaccurate citations can prevent further improper citation [ 16 ].

1. What are the root causes of citation inaccuracies?

Citation misuse can originate in literature reviews, as authors can find and choose references in arbitrary fashions. This can stem from keyword choice; many authors use broad keywords to garner a large audience, but this can hurt the number of references they receive [ 17 ]. Language can also be a barrier: one study found over 30% of systematic reviews excluded studies not published in English, which dramatically decreases the scope of literature reviews [ 18 ]. Researchers may also be biased towards articles with many citations. This can be described as the ‘Matthew effect:’ the more a paper is referenced, the more it will continue to be referenced [ 19 , 20 ]. This is concerning as citation rate of articles is not necessarily an indicator of quality or significance [ 21 ]. While papers with many citations continue to receive attention, less cited articles may be neglected, potentially hindering research advancements.

Literature reviews may also be influenced by other arbitrary factors. For example, an author's social media presence showed a positive correlation with the rate at which they were cited [ 22 , 23 ]. Another consideration for citation rate is the primacy effect, which describes how citations listed earlier in a study are used more frequently than those that appear toward the end of a study [ 24 ]. The reputation of the author(s), organization(s), journal, or country represented by a paper may also play a role in the number of times it is cited [ 25 ]. Some authors or groups of authors may receive an increased number of citations based on their production level or experience in the field of study [ 25 ]. Additionally, luck and last name may inevitably affect the rate at which someone is repeatedly cited.

2. What are examples of citation inaccuracies?

Selective citation, whether purposeful or subconscious, is an endemic problem [ 11 , 26 , 27 ]. Studies showing positive results are cited more often than those with neutral or negative results, a phenomenon known as citation bias [ 26 ]. This gives readers a biased view and overrepresents positive findings [ 26 ]. Other common forms of improper citation usage include: secondary citation, incorrect/opposite conclusion, back door invention, fact not found, and inaccurate population. Secondary citation, or “amplification,” is the act of citing a fact in a paper that was itself supported by a citation instead of going to the original article [ 16 ]. Amplification leads to the expansion of a belief without additional primary data [ 10 ]. Incorrect/opposite conclusion occurs when inaccurate or missing information is cited. Specifically, an author may cite an article presenting the opposite conclusion referred to in the study [ 16 ]. This error is especially detrimental as studies make claims contradicting the citation, yet this contradiction may be further perpetuated in future studies via amplification. “Back door invention” is the error of citing abstracts while leading the reader to believe it is a peer-reviewed article [ 10 ]. Fact not found consists of a claim that a cited article has stated a fact or statistic, when in reality did not mention it at all and is therefore unsupported [ 16 ]. Lastly, inaccurate population involves the referencing of a study which may have found the results reported, but the results obtained in the cited article may not be generalizable to the population in the new study [ 16 ]. Research has also shown that citation of retracted studies occurs in many fields and these studies are often cited positively [ [28] , [29] , [30] , [31] ]. One study showed that even after 5 years, retracted studies by an author were still being cited, with only 25% of citations acknowledging it had been retracted [ 31 ].

3. What can be done to prevent or correct citation inaccuracies?

Solutions to many of these problems have been shared [ [15] , [16] , [17] , 22 , 23 ]. Authors can help others find their research by using targeted rather than generic keywords [ 17 ]. Similarly, a social media presence by journals and authors may be warranted to improve discoverability [ 22 , 23 ]. While not feasible for all literature reviews, machine learning has been used in finding relevant references for systematic reviews [ 32 ]. In short, machine learning is a form of artificial intelligence that allows systems to create algorithms based on data received. Future improvements in machine learning may allow for widespread use in finding and citing references in a way that is both efficient and accurate. One solution that has been proposed is the development of a tool named MyCites [ 33 ]. This tool would allow for the ability to mark citations as inaccurate and have these notations travel with the digital document so that future readers are aware of the accuracy of any contested citations [ 33 ]. These capabilities may help to stifle early citation inaccuracies and prevent the amplification of inaccurate citations.

Given the prevalence of citation inaccuracies, it is imperative those involved in the peer review process review submissions with an eye toward citation accuracy. At the start, authors must thoroughly recheck their citations and verify the relevance and validity of each reference. [ 34 ] One survey showed that only 4% of published scientists regularly check citations in articles they read [ 3 ]. Some authors have suggested that a simple checklist would avoid most errors [ 16 ]. It has also been suggested that editors develop training courses for authors outlining the acceptable citation styles pertinent to a particular journal [ 34 ]. Reviewers are in the unique role of making sure that new submissions are, evidence-based, in publishable condition, and add to the current body of knowledge. Such responsibility also includes evaluating the references of these submissions and suggesting the alteration, removal, or addition of references which would ensure citation accuracy [ 34 ]. The peer review process can help correct citation mistakes, especially through increased spot checks by editors/reviewers [ 9 ]. Lastly, the publisher's role in citation accuracy has started to include the use of software to process, link, and check the quality of references. [ 35 ] The increased utilization of new technology to verify citation accuracy will be of great benefit to both researchers and readers.

We also seek to share common guidelines for proper citation. First, ensure the citation provides correct publication details, including name, article title, and journal [ 15 ]. Second, the citation must substantiate the claim [ 15 ]. Next, authors should use unbiased sources that provide reliable data [ 15 ]. Articles from prestigious journals should not be assumed as reliable; analysis of the article itself is critical [ 15 ]. Additionally, be mindful of reconciling evidence. Authors should present the information in an objective manner [ 15 ]. In research it is crucial for “evidence to guide conclusions.” [ 36 ] Citations are an important part of the scientific process. They allow researchers to support and share findings, helping to further innovation. However, citations can be misused, slowing progress in clinical research and circulating unsupported beliefs. Many problems with citations can be fixed with increased attention to detail by authors and editors, ultimately strengthening credibility of the literature.

Ethical approval

Not applicable.

Sources of funding

Author contribution.

Study design and conception: AE. Data collection, interpretation and analysis: MN, CA, AE. Manuscript preparation: MN, CA, AE, MM. Critical revision of manuscript: MN, CA, MM, AE. All authors read and approved the final manuscript.

Trial registry number

• 1. Name of the registry:
• 2. Unique Identifying number or registration ID:
• 3. Hyperlink to the registration (must be publicly accessible):

Adel Elkbuli.

Mark McKenney

Declaration of competing interest

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• Volume 110, Issue 9
• The role of COVID-19 vaccines in preventing post-COVID-19 thromboembolic and cardiovascular complications
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• Núria Mercadé-Besora 1 , 2 , 3 ,
• Xintong Li 1 ,
• Raivo Kolde 4 ,
• Nhung TH Trinh 5 ,
• Maria T Sanchez-Santos 1 ,
• Wai Yi Man 1 ,
• Elena Roel 3 ,
• Carlen Reyes 3 ,
• http://orcid.org/0000-0003-0388-3403 Antonella Delmestri 1 ,
• Hedvig M E Nordeng 6 , 7 ,
• http://orcid.org/0000-0002-4036-3856 Anneli Uusküla 8 ,
• http://orcid.org/0000-0002-8274-0357 Talita Duarte-Salles 3 , 9 ,
• Clara Prats 2 ,
• http://orcid.org/0000-0002-3950-6346 Daniel Prieto-Alhambra 1 , 9 ,
• http://orcid.org/0000-0002-0000-0110 Annika M Jödicke 1 ,
• Martí Català 1
• 1 Pharmaco- and Device Epidemiology Group, Health Data Sciences, Botnar Research Centre, NDORMS , University of Oxford , Oxford , UK
• 2 Department of Physics , Universitat Politècnica de Catalunya , Barcelona , Spain
• 3 Fundació Institut Universitari per a la recerca a l'Atenció Primària de Salut Jordi Gol i Gurina (IDIAPJGol) , IDIAP Jordi Gol , Barcelona , Catalunya , Spain
• 4 Institute of Computer Science , University of Tartu , Tartu , Estonia
• 5 Pharmacoepidemiology and Drug Safety Research Group, Department of Pharmacy, Faculty of Mathematics and Natural Sciences , University of Oslo , Oslo , Norway
• 6 School of Pharmacy , University of Oslo , Oslo , Norway
• 7 Division of Mental Health , Norwegian Institute of Public Health , Oslo , Norway
• 8 Department of Family Medicine and Public Health , University of Tartu , Tartu , Estonia
• 9 Department of Medical Informatics, Erasmus University Medical Center , Erasmus University Rotterdam , Rotterdam , Zuid-Holland , Netherlands
• Correspondence to Prof Daniel Prieto-Alhambra, Pharmaco- and Device Epidemiology Group, Health Data Sciences, Botnar Research Centre, NDORMS, University of Oxford, Oxford, UK; daniel.prietoalhambra{at}ndorms.ox.ac.uk

Objective To study the association between COVID-19 vaccination and the risk of post-COVID-19 cardiac and thromboembolic complications.

Methods We conducted a staggered cohort study based on national vaccination campaigns using electronic health records from the UK, Spain and Estonia. Vaccine rollout was grouped into four stages with predefined enrolment periods. Each stage included all individuals eligible for vaccination, with no previous SARS-CoV-2 infection or COVID-19 vaccine at the start date. Vaccination status was used as a time-varying exposure. Outcomes included heart failure (HF), venous thromboembolism (VTE) and arterial thrombosis/thromboembolism (ATE) recorded in four time windows after SARS-CoV-2 infection: 0–30, 31–90, 91–180 and 181–365 days. Propensity score overlap weighting and empirical calibration were used to minimise observed and unobserved confounding, respectively.

Fine-Gray models estimated subdistribution hazard ratios (sHR). Random effect meta-analyses were conducted across staggered cohorts and databases.

Results The study included 10.17 million vaccinated and 10.39 million unvaccinated people. Vaccination was associated with reduced risks of acute (30-day) and post-acute COVID-19 VTE, ATE and HF: for example, meta-analytic sHR of 0.22 (95% CI 0.17 to 0.29), 0.53 (0.44 to 0.63) and 0.45 (0.38 to 0.53), respectively, for 0–30 days after SARS-CoV-2 infection, while in the 91–180 days sHR were 0.53 (0.40 to 0.70), 0.72 (0.58 to 0.88) and 0.61 (0.51 to 0.73), respectively.

Conclusions COVID-19 vaccination reduced the risk of post-COVID-19 cardiac and thromboembolic outcomes. These effects were more pronounced for acute COVID-19 outcomes, consistent with known reductions in disease severity following breakthrough versus unvaccinated SARS-CoV-2 infection.

• Epidemiology
• PUBLIC HEALTH
• Electronic Health Records

Data availability statement

Data may be obtained from a third party and are not publicly available. CPRD: CPRD data were obtained under the CPRD multi-study license held by the University of Oxford after Research Data Governance (RDG) approval. Direct data sharing is not allowed. SIDIAP: In accordance with current European and national law, the data used in this study is only available for the researchers participating in this study. Thus, we are not allowed to distribute or make publicly available the data to other parties. However, researchers from public institutions can request data from SIDIAP if they comply with certain requirements. Further information is available online ( https://www.sidiap.org/index.php/menu-solicitudesen/application-proccedure ) or by contacting SIDIAP ([email protected]). CORIVA: CORIVA data were obtained under the approval of Research Ethics Committee of the University of Tartu and the patient level data sharing is not allowed. All analyses in this study were conducted in a federated manner, where analytical code and aggregated (anonymised) results were shared, but no patient-level data was transferred across the collaborating institutions.

This is an open access article distributed in accordance with the Creative Commons Attribution 4.0 Unported (CC BY 4.0) license, which permits others to copy, redistribute, remix, transform and build upon this work for any purpose, provided the original work is properly cited, a link to the licence is given, and indication of whether changes were made. See:  https://creativecommons.org/licenses/by/4.0/ .

https://doi.org/10.1136/heartjnl-2023-323483

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WHAT IS ALREADY KNOWN ON THIS TOPIC

COVID-19 vaccines proved to be highly effective in reducing the severity of acute SARS-CoV-2 infection.

While COVID-19 vaccines were associated with increased risk for cardiac and thromboembolic events, such as myocarditis and thrombosis, the risk of complications was substantially higher due to SARS-CoV-2 infection.

WHAT THIS STUDY ADDS

COVID-19 vaccination reduced the risk of heart failure, venous thromboembolism and arterial thrombosis/thromboembolism in the acute (30 days) and post-acute (31 to 365 days) phase following SARS-CoV-2 infection. This effect was stronger in the acute phase.

The overall additive effect of vaccination on the risk of post-vaccine and/or post-COVID thromboembolic and cardiac events needs further research.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

COVID-19 vaccines proved to be highly effective in reducing the risk of post-COVID cardiovascular and thromboembolic complications.

Introduction

COVID-19 vaccines were approved under emergency authorisation in December 2020 and showed high effectiveness against SARS-CoV-2 infection, COVID-19-related hospitalisation and death. 1 2 However, concerns were raised after spontaneous reports of unusual thromboembolic events following adenovirus-based COVID-19 vaccines, an association that was further assessed in observational studies. 3 4 More recently, mRNA-based vaccines were found to be associated with a risk of rare myocarditis events. 5 6

On the other hand, SARS-CoV-2 infection can trigger cardiac and thromboembolic complications. 7 8 Previous studies showed that, while slowly decreasing over time, the risk for serious complications remain high for up to a year after infection. 9 10 Although acute and post-acute cardiac and thromboembolic complications following COVID-19 are rare, they present a substantial burden to the affected patients, and the absolute number of cases globally could become substantial.

Recent studies suggest that COVID-19 vaccination could protect against cardiac and thromboembolic complications attributable to COVID-19. 11 12 However, most studies did not include long-term complications and were conducted among specific populations.

Evidence is still scarce as to whether the combined effects of COVID-19 vaccines protecting against SARS-CoV-2 infection and reducing post-COVID-19 cardiac and thromboembolic outcomes, outweigh any risks of these complications potentially associated with vaccination.

We therefore used large, representative data sources from three European countries to assess the overall effect of COVID-19 vaccines on the risk of acute and post-acute COVID-19 complications including venous thromboembolism (VTE), arterial thrombosis/thromboembolism (ATE) and other cardiac events. Additionally, we studied the comparative effects of ChAdOx1 versus BNT162b2 on the risk of these same outcomes.

Data sources

We used four routinely collected population-based healthcare datasets from three European countries: the UK, Spain and Estonia.

For the UK, we used data from two primary care databases—namely, Clinical Practice Research Datalink, CPRD Aurum 13 and CPRD Gold. 14 CPRD Aurum currently covers 13 million people from predominantly English practices, while CPRD Gold comprises 3.1 million active participants mostly from GP practices in Wales and Scotland. Spanish data were provided by the Information System for the Development of Research in Primary Care (SIDIAP), 15 which encompasses primary care records from 6 million active patients (around 75% of the population in the region of Catalonia) linked to hospital admissions data (Conjunt Mínim Bàsic de Dades d’Alta Hospitalària). Finally, the CORIVA dataset based on national health claims data from Estonia was used. It contains all COVID-19 cases from the first year of the pandemic and ~440 000 randomly selected controls. CORIVA was linked to the death registry and all COVID-19 testing from the national health information system.

Databases included sociodemographic information, diagnoses, measurements, prescriptions and secondary care referrals and were linked to vaccine registries, including records of all administered vaccines from all healthcare settings. Data availability for CPRD Gold ended in December 2021, CPRD Aurum in January 2022, SIDIAP in June 2022 and CORIVA in December 2022.

All databases were mapped to the Observational Medical Outcomes Partnership Common Data Model (OMOP CDM) 16 to facilitate federated analytics.

Multinational network staggered cohort study: study design and participants

The study design has been published in detail elsewhere. 17 Briefly, we used a staggered cohort design considering vaccination as a time-varying exposure. Four staggered cohorts were designed with each cohort representing a country-specific vaccination rollout phase (eg, dates when people became eligible for vaccination, and eligibility criteria).

The source population comprised all adults registered in the respective database for at least 180 days at the start of the study (4 January 2021 for CPRD Gold and Aurum, 20 February 2021 for SIDIAP and 28 January 2021 for CORIVA). Subsequently, each staggered cohort corresponded to an enrolment period: all people eligible for vaccination during this time were included in the cohort and people with a history of SARS-CoV-2 infection or COVID-19 vaccination before the start of the enrolment period were excluded. Across countries, cohort 1 comprised older age groups, whereas cohort 2 comprised individuals at risk for severe COVID-19. Cohort 3 included people aged ≥40 and cohort 4 enrolled people aged ≥18.

In each cohort, people receiving a first vaccine dose during the enrolment period were allocated to the vaccinated group, with their index date being the date of vaccination. Individuals who did not receive a vaccine dose comprised the unvaccinated group and their index date was assigned within the enrolment period, based on the distribution of index dates in the vaccinated group. People with COVID-19 before the index date were excluded.

Follow-up started from the index date until the earliest of end of available data, death, change in exposure status (first vaccine dose for those unvaccinated) or outcome of interest.

COVID-19 vaccination

All vaccines approved within the study period from January 2021 to July 2021—namely, ChAdOx1 (Oxford/AstraZeneca), BNT162b2 (BioNTech/Pfizer]) Ad26.COV2.S (Janssen) and mRNA-1273 (Moderna), were included for this study.

Post-COVID-19 outcomes of interest

Outcomes of interest were defined as SARS-CoV-2 infection followed by a predefined thromboembolic or cardiac event of interest within a year after infection, and with no record of the same clinical event in the 6 months before COVID-19. Outcome date was set as the corresponding SARS-CoV-2 infection date.

COVID-19 was identified from either a positive SARS-CoV-2 test (polymerase chain reaction (PCR) or antigen), or a clinical COVID-19 diagnosis, with no record of COVID-19 in the previous 6 weeks. This wash-out period was imposed to exclude re-recordings of the same COVID-19 episode.

Post-COVID-19 outcome events were selected based on previous studies. 11–13 Events comprised ischaemic stroke (IS), haemorrhagic stroke (HS), transient ischaemic attack (TIA), ventricular arrhythmia/cardiac arrest (VACA), myocarditis/pericarditis (MP), myocardial infarction (MI), heart failure (HF), pulmonary embolism (PE) and deep vein thrombosis (DVT). We used two composite outcomes: (1) VTE, as an aggregate of PE and DVT and (2) ATE, as a composite of IS, TIA and MI. To avoid re-recording of the same complication we imposed a wash-out period of 90 days between records. Phenotypes for these complications were based on previously published studies. 3 4 8 18

All outcomes were ascertained in four different time periods following SARS-CoV-2 infection: the first period described the acute infection phase—that is, 0–30 days after COVID-19, whereas the later periods - which are 31–90 days, 91–180 days and 181–365 days, illustrate the post-acute phase ( figure 1 ).

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Study outcome design. Study outcomes of interest are defined as a COVID-19 infection followed by one of the complications in the figure, within a year after infection. Outcomes were ascertained in four different time windows after SARS-CoV-2 infection: 0–30 days (namely the acute phase), 31–90 days, 91–180 days and 181–365 days (these last three comprise the post-acute phase).

Negative control outcomes

Negative control outcomes (NCOs) were used to detect residual confounding. NCOs are outcomes which are not believed to be causally associated with the exposure, but share the same bias structure with the exposure and outcome of interest. Therefore, no significant association between exposure and NCO is to be expected. Our study used 43 different NCOs from previous work assessing vaccine effectiveness. 19

Statistical analysis

Federated network analyses.

A template for an analytical script was developed and subsequently tailored to include the country-specific aspects (eg, dates, priority groups) for the vaccination rollout. Analyses were conducted locally for each database. Only aggregated data were shared and person counts <5 were clouded.

Propensity score weighting

Large-scale propensity scores (PS) were calculated to estimate the likelihood of a person receiving the vaccine based on their demographic and health-related characteristics (eg, conditions, medications) prior to the index date. PS were then used to minimise observed confounding by creating a weighted population (overlap weighting 20 ), in which individuals contributed with a different weight based on their PS and vaccination status.

Prespecified key variables included in the PS comprised age, sex, location, index date, prior observation time in the database, number of previous outpatient visits and previous SARS-CoV-2 PCR/antigen tests. Regional vaccination, testing and COVID-19 incidence rates were also forced into the PS equation for the UK databases 21 and SIDIAP. 22 In addition, least absolute shrinkage and selection operator (LASSO) regression, a technique for variable selection, was used to identify additional variables from all recorded conditions and prescriptions within 0–30 days, 31–180 days and 181-any time (conditions only) before the index date that had a prevalence of >0.5% in the study population.

PS were then separately estimated for each staggered cohort and analysis. We considered covariate balance to be achieved if absolute standardised mean differences (ASMDs) were ≤0.1 after weighting. Baseline characteristics such as demographics and comorbidities were reported.

Effect estimation

To account for the competing risk of death associated with COVID-19, Fine-and-Grey models 23 were used to calculate subdistribution hazard ratios (sHRs). Subsequently, sHRs and confidence intervals were empirically calibrated from NCO estimates 24 to account for unmeasured confounding. To calibrate the estimates, the empirical null distribution was derived from NCO estimates and was used to compute calibrated confidence intervals. For each outcome, sHRs from the four staggered cohorts were pooled using random-effect meta-analysis, both separately for each database and across all four databases.

Sensitivity analysis

Sensitivity analyses comprised 1) censoring follow-up for vaccinated people at the time when they received their second vaccine dose and 2) considering only the first post-COVID-19 outcome within the year after infection ( online supplemental figure S1 ). In addition, comparative effectiveness analyses were conducted for BNT162b2 versus ChAdOx1.

Supplemental material

Data and code availability.

All analytic code for the study is available in GitHub ( https://github.com/oxford-pharmacoepi/vaccineEffectOnPostCovidCardiacThromboembolicEvents ), including code lists for vaccines, COVID-19 tests and diagnoses, cardiac and thromboembolic events, NCO and health conditions to prioritise patients for vaccination in each country. We used R version 4.2.3 and statistical packages survival (3.5–3), Empirical Calibration (3.1.1), glmnet (4.1-7), and Hmisc (5.0–1).

Patient and public involvement

Owing to the nature of the study and the limitations regarding data privacy, the study design, analysis, interpretation of data and revision of the manuscript did not involve any patients or members of the public.

All aggregated results are available in a web application ( https://dpa-pde-oxford.shinyapps.io/PostCovidComplications/ ).

We included over 10.17 million vaccinated individuals (1 618 395 from CPRD Gold; 5 729 800 from CPRD Aurum; 2 744 821 from SIDIAP and 77 603 from CORIVA) and 10.39 million unvaccinated individuals (1 640 371; 5 860 564; 2 588 518 and 302 267, respectively). Online supplemental figures S2-5 illustrate study inclusion for each database.

Adequate covariate balance was achieved after PS weighting in most studies: CORIVA (all cohorts) and SIDIAP (cohorts 1 and 4) did not contribute to ChAdOx1 subanalyses owing to sample size and covariate imbalance. ASMD results are accessible in the web application.

NCO analyses suggested residual bias after PS weighting, with a majority of NCOs associated positively with vaccination. Therefore, calibrated estimates are reported in this manuscript. Uncalibrated effect estimates and NCO analyses are available in the web interface.

Population characteristics

Table 1 presents baseline characteristics for the weighted populations in CPRD Aurum, for illustrative purposes. Online supplemental tables S1-25 summarise baseline characteristics for weighted and unweighted populations for each database and comparison. Across databases and cohorts, populations followed similar patterns: cohort 1 represented an older subpopulation (around 80 years old) with a high proportion of women (57%). Median age was lowest in cohort 4 ranging between 30 and 40 years.

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Characteristics of weighted populations in CPRD Aurum database, stratified by staggered cohort and exposure status. Exposure is any COVID-19 vaccine

COVID-19 vaccination and post-COVID-19 complications

Table 2 shows the incidence of post-COVID-19 VTE, ATE and HF, the three most common post-COVID-19 conditions among the studied outcomes. Outcome counts are presented separately for 0–30, 31–90, 91–180 and 181–365 days after SARS-CoV-2 infection. Online supplemental tables S26-36 include all studied complications, also for the sensitivity and subanalyses. Similar pattern for incidences were observed across all databases: higher outcome rates in the older populations (cohort 1) and decreasing frequency with increasing time after infection in all cohorts.

Number of records (and risk per 10 000 individuals) for acute and post-acute COVID-19 cardiac and thromboembolic complications, across cohorts and databases for any COVID-19 vaccination

Forest plots for the effect of COVID-19 vaccines on post-COVID-19 cardiac and thromboembolic complications; meta-analysis across cohorts and databases. Dashed line represents a level of heterogeneity I 2 >0.4. ATE, arterial thrombosis/thromboembolism; CD+HS, cardiac diseases and haemorrhagic stroke; VTE, venous thromboembolism.

Results from calibrated estimates pooled in meta-analysis across cohorts and databases are shown in figure 2 .

Reduced risk associated with vaccination is observed for acute and post-acute VTE, DVT, and PE: acute meta-analytic sHR are 0.22 (95% CI, 0.17–0.29); 0.36 (0.28–0.45); and 0.19 (0.15–0.25), respectively. For VTE in the post-acute phase, sHR estimates are 0.43 (0.34–0.53), 0.53 (0.40–0.70) and 0.50 (0.36–0.70) for 31–90, 91–180, and 181–365 days post COVID-19, respectively. Reduced risk of VTE outcomes was observed in vaccinated across databases and cohorts, see online supplemental figures S14–22 .

Similarly, the risk of ATE, IS and MI in the acute phase after infection was reduced for the vaccinated group, sHR of 0.53 (0.44–0.63), 0.55 (0.43–0.70) and 0.49 (0.38–0.62), respectively. Reduced risk associated with vaccination persisted for post-acute ATE, with sHR of 0.74 (0.60–0.92), 0.72 (0.58–0.88) and 0.62 (0.48–0.80) for 31–90, 91–180 and 181–365 days post-COVID-19, respectively. Risk of post-acute MI remained lower for vaccinated in the 31–90 and 91–180 days after COVID-19, with sHR of 0.64 (0.46–0.87) and 0.64 (0.45–0.90), respectively. Vaccination effect on post-COVID-19 TIA was seen only in the 181–365 days, with sHR of 0.51 (0.31–0.82). Online supplemental figures S23-31 show database-specific and cohort-specific estimates for ATE-related complications.

Risk of post-COVID-19 cardiac complications was reduced in vaccinated individuals. Meta-analytic estimates in the acute phase showed sHR of 0.45 (0.38–0.53) for HF, 0.41 (0.26–0.66) for MP and 0.41 (0.27–0.63) for VACA. Reduced risk persisted for post-acute COVID-19 HF: sHR 0.61 (0.51–0.73) for 31–90 days, 0.61 (0.51–0.73) for 91–180 days and 0.52 (0.43–0.63) for 181–365 days. For post-acute MP, risk was only lowered in the first post-acute window (31–90 days), with sHR of 0.43 (0.21–0.85). Vaccination showed no association with post-COVID-19 HS. Database-specific and cohort-specific results for these cardiac diseases are shown in online supplemental figures S32-40 .

Stratified analyses by vaccine showed similar associations, except for ChAdOx1 which was not associated with reduced VTE and ATE risk in the last post-acute window. Sensitivity analyses were consistent with main results ( online supplemental figures S6-13 ).

Figure 3 shows the results of comparative effects of BNT162b2 versus ChAdOx1, based on UK data. Meta-analytic estimates favoured BNT162b2 (sHR of 0.66 (0.46–0.93)) for VTE in the 0–30 days after infection, but no differences were seen for post-acute VTE or for any of the other outcomes. Results from sensitivity analyses, database-specific and cohort-specific estimates were in line with the main findings ( online supplemental figures S41-51 ).

Forest plots for comparative vaccine effect (BNT162b2 vs ChAdOx1); meta-analysis across cohorts and databases. ATE, arterial thrombosis/thromboembolism; CD+HS, cardiac diseases and haemorrhagic stroke; VTE, venous thromboembolism.

Key findings

Our analyses showed a substantial reduction of risk (45–81%) for thromboembolic and cardiac events in the acute phase of COVID-19 associated with vaccination. This finding was consistent across four databases and three different European countries. Risks for post-acute COVID-19 VTE, ATE and HF were reduced to a lesser extent (24–58%), whereas a reduced risk for post-COVID-19 MP and VACA in vaccinated people was seen only in the acute phase.

Results in context

The relationship between SARS-CoV-2 infection, COVID-19 vaccines and thromboembolic and/or cardiac complications is tangled. Some large studies report an increased risk of VTE and ATE following both ChAdOx1 and BNT162b2 vaccination, 7 whereas other studies have not identified such a risk. 25 Elevated risk of VTE has also been reported among patients with COVID-19 and its occurrence can lead to poor prognosis and mortality. 26 27 Similarly, several observational studies have found an association between COVID-19 mRNA vaccination and a short-term increased risk of myocarditis, particularly among younger male individuals. 5 6 For instance, a self-controlled case series study conducted in England revealed about 30% increased risk of hospital admission due to myocarditis within 28 days following both ChAdOx1 and BNT162b2 vaccines. However, this same study also found a ninefold higher risk for myocarditis following a positive SARS-CoV-2 test, clearly offsetting the observed post-vaccine risk.

COVID-19 vaccines have demonstrated high efficacy and effectiveness in preventing infection and reducing the severity of acute-phase infection. However, with the emergence of newer variants of the virus, such as omicron, and the waning protective effect of the vaccine over time, there is a growing interest in understanding whether the vaccine can also reduce the risk of complications after breakthrough infections. Recent studies suggested that COVID-19 vaccination could potentially protect against acute post-COVID-19 cardiac and thromboembolic events. 11 12 A large prospective cohort study 11 reports risk of VTE after SARS-CoV-2 infection to be substantially reduced in fully vaccinated ambulatory patients. Likewise, Al-Aly et al 12 suggest a reduced risk for post-acute COVID-19 conditions in breakthrough infection versus SARS-CoV-2 infection without prior vaccination. However, the populations were limited to SARS-CoV-2 infected individuals and estimates did not include the effect of the vaccine to prevent COVID-19 in the first place. Other studies on post-acute COVID-19 conditions and symptoms have been conducted, 28 29 but there has been limited reporting on the condition-specific risks associated with COVID-19, even though the prognosis for different complications can vary significantly.

In line with previous studies, our findings suggest a potential benefit of vaccination in reducing the risk of post-COVID-19 thromboembolic and cardiac complications. We included broader populations, estimated the risk in both acute and post-acute infection phases and replicated these using four large independent observational databases. By pooling results across different settings, we provided the most up-to-date and robust evidence on this topic.

Strengths and limitations

The study has several strengths. Our multinational study covering different healthcare systems and settings showed consistent results across all databases, which highlights the robustness and replicability of our findings. All databases had complete recordings of vaccination status (date and vaccine) and are representative of the respective general population. Algorithms to identify study outcomes were used in previous published network studies, including regulatory-funded research. 3 4 8 18 Other strengths are the staggered cohort design which minimises confounding by indication and immortal time bias. PS overlap weighting and NCO empirical calibration have been shown to adequately minimise bias in vaccine effectiveness studies. 19 Furthermore, our estimates include the vaccine effectiveness against COVID-19, which is crucial in the pathway to experience post-COVID-19 complications.

Our study has some limitations. The use of real-world data comes with inherent limitations including data quality concerns and risk of confounding. To deal with these limitations, we employed state-of-the-art methods, including large-scale propensity score weighting and calibration of effect estimates using NCO. 19 24 A recent study 30 has demonstrated that methodologically sound observational studies based on routinely collected data can produce results similar to those of clinical trials. We acknowledge that results from NCO were positively associated with vaccination, and estimates might still be influenced by residual bias despite using calibration. Another limitation is potential under-reporting of post-COVID-19 complications: some asymptomatic and mild COVID-19 infections might have not been recorded. Additionally, post-COVID-19 outcomes of interest might be under-recorded in primary care databases (CPRD Aurum and Gold) without hospital linkage, which represent a large proportion of the data in the study. However, results in SIDIAP and CORIVA, which include secondary care data, were similar. Also, our study included a small number of young men and male teenagers, who were the main population concerned with increased risks of myocarditis/pericarditis following vaccination.

Conclusions

Vaccination against SARS-CoV-2 substantially reduced the risk of acute post-COVID-19 thromboembolic and cardiac complications, probably through a reduction in the risk of SARS-CoV-2 infection and the severity of COVID-19 disease due to vaccine-induced immunity. Reduced risk in vaccinated people lasted for up to 1 year for post-COVID-19 VTE, ATE and HF, but not clearly for other complications. Findings from this study highlight yet another benefit of COVID-19 vaccination. However, further research is needed on the possible waning of the risk reduction over time and on the impact of booster vaccination.

Ethics statements

Patient consent for publication.

Not applicable.

Ethics approval

The study was approved by the CPRD’s Research Data Governance Process, Protocol No 21_000557 and the Clinical Research Ethics committee of Fundació Institut Universitari per a la recerca a l’Atenció Primària de Salut Jordi Gol i Gurina (IDIAPJGol) (approval number 4R22/133) and the Research Ethics Committee of the University of Tartu (approval No. 330/T-10).

Acknowledgments

This study is based in part on data from the Clinical Practice Research Datalink (CPRD) obtained under licence from the UK Medicines and Healthcare products Regulatory Agency. We thank the patients who provided these data, and the NHS who collected the data as part of their care and support. All interpretations, conclusions and views expressed in this publication are those of the authors alone and not necessarily those of CPRD. We would also like to thank the healthcare professionals in the Catalan healthcare system involved in the management of COVID-19 during these challenging times, from primary care to intensive care units; the Institut de Català de la Salut and the Program d’Analítica de Dades per a la Recerca i la Innovació en Salut for providing access to the different data sources accessible through The System for the Development of Research in Primary Care (SIDIAP).

• Pritchard E ,
• Matthews PC ,
• Stoesser N , et al
• Lauring AS ,
• Tenforde MW ,
• Chappell JD , et al
• Pistillo A , et al
• Duarte-Salles T , et al
• Hansen JV ,
• Fosbøl E , et al
• Chen A , et al
• Hippisley-Cox J ,
• Mei XW , et al
• Duarte-Salles T ,
• Fernandez-Bertolin S , et al
• Ip S , et al
• Bowe B , et al
• Prats-Uribe A ,
• Feng Q , et al
• Campbell J , et al
• Herrett E ,
• Gallagher AM ,
• Bhaskaran K , et al
• Raventós B ,
• Fernández-Bertolín S ,
• Aragón M , et al
• Makadia R ,
• Matcho A , et al
• Mercadé-Besora N ,
• Kolde R , et al
• Ostropolets A ,
• Makadia R , et al
• Rathod-Mistry T , et al
• Thomas LE ,
• ↵ Coronavirus (COVID-19) in the UK . 2022 . Available : https://coronavirus.data.gov.uk/
• Generalitat de Catalunya
• Schuemie MJ ,
• Hripcsak G ,
• Ryan PB , et al
• Houghton DE ,
• Wysokinski W ,
• Casanegra AI , et al
• Katsoularis I ,
• Fonseca-Rodríguez O ,
• Farrington P , et al
• Jehangir Q ,
• Li P , et al
• Byambasuren O ,
• Stehlik P ,
• Clark J , et al
• Brannock MD ,
• Preiss AJ , et al
• Schneeweiss S , RCT-DUPLICATE Initiative , et al

Supplementary materials

Supplementary data.

This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

• Data supplement 1

AMJ and MC are joint senior authors.

Contributors DPA and AMJ led the conceptualisation of the study with contributions from MC and NM-B. AMJ, TD-S, ER, AU and NTHT adapted the study design with respect to the local vaccine rollouts. AD and WYM mapped and curated CPRD data. MC and NM-B developed code with methodological contributions advice from MTS-S and CP. DPA, MC, NTHT, TD-S, HMEN, XL, CR and AMJ clinically interpreted the results. NM-B, XL, AMJ and DPA wrote the first draft of the manuscript, and all authors read, revised and approved the final version. DPA and AMJ obtained the funding for this research. DPA is responsible for the overall content as guarantor: he accepts full responsibility for the work and the conduct of the study, had access to the data, and controlled the decision to publish.

Funding The research was supported by the National Institute for Health and Care Research (NIHR) Oxford Biomedical Research Centre (BRC). DPA is funded through a NIHR Senior Research Fellowship (Grant number SRF-2018–11-ST2-004). Funding to perform the study in the SIDIAP database was provided by the Real World Epidemiology (RWEpi) research group at IDIAPJGol. Costs of databases mapping to OMOP CDM were covered by the European Health Data and Evidence Network (EHDEN).

Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting or dissemination plans of this research.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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Clinical Benefit and Regulatory Outcomes of Cancer Drugs Receiving Accelerated Approval

• 1 Program on Regulation, Therapeutics, and Law, Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
• Original Investigation Therapeutic Value of Drugs Granted Accelerated Approval or Conditional Marketing Authorization Kerstin N. Vokinger, MD, JD, PhD, LLM; Aaron S. Kesselheim, MD, JD, MPH; Camille E. G. Glaus, BSc, JD, LLM; Thomas J. Hwang, MD JAMA Health Forum
• Research Letter Exposure to Cancer Drugs Without Confirmed Benefit After FDA Accelerated Approval Ravi B. Parikh, MD, MPP; Rebecca A. Hubbard, PhD; Erkuan Wang, MA; Trevor J. Royce, MD, MPH; Aaron B. Cohen, MD, MSCE; Amy S. Clark, MD, MSCE; Ronac Mamtani, MD, MSCE JAMA Oncology
• Research Letter Time to Confirmatory Study Initiation After Accelerated Approval of Drugs in the US Shelley A. Jazowski, PhD, MPH; Avi U. Vaidya, MPH; Julie M. Donohue, PhD; Stacie B. Dusetzina, PhD; Rachel E. Sachs, JD, MPH JAMA Internal Medicine
• Original Investigation NCCN Recommendations of Cancer Drugs Edward R. Scheffer Cliff, MBBS, MPH; Rachel S. Rome, MD; Aaron S. Kesselheim, MD, JD, MPH; Benjamin N. Rome, MD, MPH JAMA Network Open

Question   What is the clinical benefit of cancer drugs granted accelerated approval, and on what basis are they converted to regular approval?

Findings   In this cohort study of cancer drugs granted accelerated approval from 2013 to 2017, 41% (19/46) did not improve overall survival or quality of life in confirmatory trials after more than 5 years of follow-up, with results not yet available for another 15% (7/46). Among drugs converted to regular approval, 60% (29/48) of conversions relied on surrogate measures.

Meaning   Although accelerated approval can be useful, some cancer drugs do not end up demonstrating benefit in extending patients’ lives or improving their quality of life.

Importance   The US Food and Drug Administration’s (FDA) accelerated approval pathway allows approval of investigational drugs treating unmet medical needs based on changes to surrogate measures considered “reasonably likely” to predict clinical benefit. Postapproval clinical trials are then required to confirm whether these drugs offer clinical benefit.

Objective   To determine whether cancer drugs granted accelerated approval ultimately demonstrate clinical benefit and to evaluate the basis of conversion to regular approval.

Design, Setting, and Participants   In this cohort study, publicly available FDA data were used to identify cancer drugs granted accelerated approval from 2013 to 2023.

Main Outcomes and Measures   Demonstrated improvement in quality of life or overall survival in accelerated approvals with more than 5 years of follow-up, as well as confirmatory trial end points and time to conversion for drug-indication pairs converted to regular approval.

Results   A total of 129 cancer drug–indication pairs were granted accelerated approval from 2013 to 2023. Among 46 indications with more than 5 years of follow-up (approved 2013-2017), approximately two-thirds (29, 63%) were converted to regular approval, 10 (22%) were withdrawn, and 7 (15%) remained ongoing after a median of 6.3 years. Fewer than half (20/46, 43%) demonstrated a clinical benefit in confirmatory trials. Time to withdrawal decreased from 9.9 years to 3.6 years, and time to regular approval increased from 1.6 years to 3.6 years. Among 48 drug-indication pairs converted to regular approval, 19 (40%) were converted based on overall survival, 21 (44%) on progression-free survival, 5 (10%) on response rate plus duration of response, 2 (4%) on response rate, and 1 (2%) despite a negative confirmatory trial. Comparing accelerated and regular approval indications, 18 of 48 (38%) were unchanged, while 30 of 48 (63%) had different indications (eg, earlier line of therapy).

Conclusions and Relevance   Most cancer drugs granted accelerated approval did not demonstrate benefit in overall survival or quality of life within 5 years of accelerated approval. Patients should be clearly informed about the cancer drugs that use the accelerated approval pathway and do not end up showing benefits in patient-centered clinical outcomes.

Read More About

Liu ITT , Kesselheim AS , Cliff ERS. Clinical Benefit and Regulatory Outcomes of Cancer Drugs Receiving Accelerated Approval. JAMA. Published online April 07, 2024. doi:10.1001/jama.2024.2396

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Computer Science > Computation and Language

Title: toward a theory of tokenization in llms.

Abstract: While there has been a large body of research attempting to circumvent tokenization for language modeling (Clark et al., 2022; Xue et al., 2022), the current consensus is that it is a necessary initial step for designing state-of-the-art performant language models. In this paper, we investigate tokenization from a theoretical point of view by studying the behavior of transformers on simple data generating processes. When trained on data drawn from certain simple $k^{\text{th}}$-order Markov processes for $k > 1$, transformers exhibit a surprising phenomenon - in the absence of tokenization, they empirically fail to learn the right distribution and predict characters according to a unigram model (Makkuva et al., 2024). With the addition of tokenization, however, we empirically observe that transformers break through this barrier and are able to model the probabilities of sequences drawn from the source near-optimally, achieving small cross-entropy loss. With this observation as starting point, we study the end-to-end cross-entropy loss achieved by transformers with and without tokenization. With the appropriate tokenization, we show that even the simplest unigram models (over tokens) learnt by transformers are able to model the probability of sequences drawn from $k^{\text{th}}$-order Markov sources near optimally. Our analysis provides a justification for the use of tokenization in practice through studying the behavior of transformers on Markovian data.

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