evidence: Following implementation of vaccination, cases of anaphylaxis after administration of the Pfizer-BioNTech and Moderna vaccines began to be reported.3,4 Anaphylaxis is a life-threatening allergic reaction that can occur after vaccination, with onset typically within minutes to hours.5 The initial estimated reporting rates for anaphylaxis in the US were 11.1 cases per million doses administered of the Pfizer-BioNTech vaccine (December 14-23, 2020) and 2.5 cases per million doses administered of the Moderna vaccine (December 21, 2020-January 10, 2021).3,4 Since these early estimates were generated, millions more doses of both vaccines have been administered and safety monitoring has detected additional cases of anaphylaxis. This analysis updates the reporting rates of anaphylaxis in individuals following receipt of either the Pfizer-BioNTech or Moderna vaccine. [...] Continued safety monitoring of mRNA COVID-19 vaccines in the US has confirmed that anaphylaxis following vaccination is a rare event, with rates of 4.7 cases/million Pfizer-BioNTech vaccine doses administered and 2.5 cases/million Moderna vaccine doses administered, based on information through January 18, 2021. When considered in the context of morbidity and mortality from COVID-19,9 the benefits of vaccination far outweigh the risk of anaphylaxis, which is treatable. Because of the acute, life-threatening nature of anaphylaxis, immediate epinephrine administration is indicated for all cases. CDC guidance on use of mRNA COVID-19 vaccines8 and management of anaphylaxis is available.10 All facilities administering COVID-19 vaccines should have the necessary supplies and trained medical personnel available to manage anaphylaxis. [...] N. Allergic reactions including anaphylaxis after receipt of the first dose of Pfizer-BioNTech COVID-19 vaccine.