Allergic reactions to vaccines, in general, are rare, with the incidence of anaphylaxis estimated at 1.31 in 1 million doses given. 1 Recent immediate allergic reactions clinically compatible with anaphylaxis have occurred in recipients of both the Pfizer-BioNTech and Moderna mRNA vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). At present, the specific mechanisms and inciting antigen/agents have not been identified.The January 6, 2021, Morbidity and Mortality Weekly Report 2 summarized the reported allergic reactions (including anaphylaxis) after receipt of the first dose of Pfizer-BioNTech coronavirus disease 2019 (COVID-19) vaccine in the United States from December 14, 2020, to December 23, 2020. During that period, monitoring by the Vaccine Adverse Event Reporting System detected 21 adverse events identified as anaphylaxis after administration of a reported 1,893,360 first doses of the Pfizer-BioNTech COVID-19 vaccine (11.1 cases per million doses); 71% of these occurred within 15 minutes of vaccination.

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