Allergic reactions to mRNA vaccines
Of nearly 65,000 employees of a Boston hospital system who received their first dose of the Pfizer-BioNTech or Moderna mRNA vaccine during the first 2 months of U.S. vaccinations, 2.1% reported acute allergic reactions. These included itching or rash not at the injection site, respiratory symptoms, hives, and swelling. There were 16 cases of confirmed anaphylaxis (rate: 0.027% with Pfizer-BioNTech, 0.023% with Moderna). Of these, 94% were female, the mean age was 41 years, 63% had a history of allergy, and 31% had a history of anaphylaxis. The mean time until anaphylaxis onset was 17 minutes. All patients recovered. Writing in JAMA, researchers note, “The overall risk of anaphylaxis to an mRNA COVID-19 vaccine remains extremely low and largely comparable to other common health care exposures.”