(HealthDay News) — Severe reactions consistent with anaphylaxis have occurred among 2.47 per 10,000 health care workers receiving COVID-19 vaccinations, according to a research letter published online in the Journal of the American Medical Association.

Kimberly G. Blumenthal, MD, from The Mongan Institute at Massachusetts General Hospital in Boston, and colleagues analyzed data from Massachusetts General Brigham employees who received their first dose of an mRNA COVID-19 vaccine (Dec. 16, 2020, to Feb. 12, 2021, with follow-up through Feb. 18, 2021) to assess acute allergic reactions.

Based on 52,805 employees who completed a symptom survey, the researchers report that 2.1% of employees had an acute allergic reaction. Reactions were more frequently reported with the Moderna vaccine versus the Pfizer-BioNTech vaccine (2.20 vs 1.95%t). Anaphylaxis was confirmed in 16 employees (0.025%), including 7 cases with the Pfizer-BioNTech vaccine (0.027%) and 9 cases with the Moderna vaccine (0.023%). The mean age among individuals with anaphylaxis was 41 years, with the majority being female (15 patients; 94%). Ten individuals with anaphylaxis (63%) had a prior allergy history and 5 (31%) had an anaphylaxis history. Mean time to onset of anaphylaxis was 17 minutes. All anaphylaxis patients recovered, with one admitted to intensive care and 9 (56%) receiving intramuscular epinephrine. Three individuals with prior anaphylaxis history did not seek care.

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“The incidence rate of confirmed anaphylaxis in this study is larger than that reported by the Centers for Disease Control and Prevention,” the authors write. “However, the overall risk of anaphylaxis to an mRNA COVID-19 vaccine remains extremely low.”


Blumenthal KG, Robinson LB, Camargo Jr CA, et al. Acute allergic reactions to mRNA COVID-19 vaccines.
JAMA. Published online March 8, 2021. doi:10.1001/jama.2021.3976