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This fact brief was originally published as an experiment to test the concepts behind fact briefs.

Readers should be aware that while there is still a lot of useful information in fact briefs like this one, not all of them reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date, don't hesitate to contact us at support@gigafact.org.

FACT BRIEF

Is the incidence of anaphylaxis from COVID-19 vaccines higher than initially thought?

Thursday, September 9, 2021

By Austin Tannenbaum

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While one study of limited scope found an unusually high incidence of anaphylaxis in COVID-19 vaccine recipients, the authoritative source on adverse vaccination events found an incidence in line with the Centers for Disease Control’s figure of “approximately 2 to 5 people per million” for life-threatening allergic reactions.

The outlier study was limited to fewer than 65,000 employees at a Massachusetts hospital. Sixteen experienced anaphylaxis — a rate of two per ten thousand. Two-thirds of those who did “had an allergy history”—a known risk multiplier.

In a much broader study, the Vaccine Adverse Event Reporting System, a government vaccine safety mechanism that requires health care professionals to report adverse effects, documented 66 anaphylaxis cases out of more than 17.5 million vaccine doses—a rate of approximately four per million.

Providers monitor recipients following vaccination. Epinephrine, the first-line treatment for anaphylaxis, is kept on hand.

This fact brief is responsive to conversations such as this one.

Sources

Centers for Disease Control Selected adverse events reported after COVID-19 vaccination

JAMA Network Acute allergic reactions to mRNA COVID-19 vaccines

JAMA Network Reports of anaphylaxis after receipt of mRNA COVID-19 vaccines in the US—December 14, 2020-January 18, 2021

Centers for Disease Control Management of anaphylaxis at COVID-19 vaccination sites

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Gigafact

Between 2020 and 2022, under close editorial supervision, Gigafact contracted a group of freelance writers and editors to test the concepts for fact briefs and provide inputs to our software development process. We call this effort Gigafact Foundry. Over the course of these two years, Gigafact Foundry writers published over 1500 fact briefs in response to claims they found online. Their important work forms the basis of Gigafact formats and editorial guidelines, and is available to the public on Gigafact.org. Readers should be aware that while there is still a lot of relevant information to be found, not all fact briefs produced by Gigafact Foundry reflect Gigafact's current methods and standards for fact briefs. If you come across any that you feel are out of date and need to be looked at with fresh eyes, don't hesitate to contact us at support@gigafact.org.

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Fact briefs are short, credibly sourced summaries that offer “yes/no” answers in response to claims found online. They rely on publicly available, often primary source data and documents. Fact briefs are created by contributors to Gigafact —a nonprofit project looking to expand participation in fact-checking and protect the democratic process. See all fact briefs here.