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Low Anaphylaxis Risk with COVID mRNA Vaccines

Mar 12, 2021 11:04 am

JAMA reports a safety survey of hospital employees showing that the risk of anaphylaxis from mRNA vaccines is 2.47 per 10,000 individuals. 

Prior studies suggested the risk of anaphylaxis to the mRNA COVID-19 vaccines may be as low as 2.5 - 11.1 cases per million doses and that such reactions are more likely in those with a history of allergy.

A prospective, post-vaccination survey study of two Boston hospital employees receiving mRNA COVID-19 vaccines between December 16th and February 12th (with follow-up 2/18/2021) were assessed for side effects, including anaphylaxis (defined by apriori criteria)

A total of 64 900 employees who received their first dose of a COVID-19 vaccine (40% Pfizer-BioNTech vaccine and 60% Moderna vaccine).

Notable side effects reported: 

  • 2.1%  Acute allergic reactions (Moderna 2.2%; Pfizer 1.95%)
  • 16 (0.025%) employees had confirmed anaphylaxis (7 cases with Pfizer-BioNTech; 9 cases Moderna vaccine) 
    • anaphylaxis occured mostly (94%) in women, 63% had a prior allergy and 5 (31%) had an anaphylaxis history.
    • Mean time to anaphylaxis onset was 17 minutes (range, 1-120).
    • All recovered and one patient was admitted to intensive care
  • It was estimated that nearly 4000 individuals with severe food or medication allergy histories were safely vaccinated.


The author has no conflicts of interest to disclose related to this subject

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