Case series/case reports (Indigo)
In December 2020, the US Food and Drug Administration (FDA) issued Emergency Use Authorisations for two mRNA-based vaccines for prevention of coronavirus disease 2019 (COVID-19): Pfizer-BioNTech COVID-19 vaccine (EUA issued December 11; 2 doses, 3 weeks apart) and Moderna COVID-19 vaccine (EUA issued December 18; 2 doses, 1 month apart). Shortly after each authorisation, the Advisory Committee on Immunization Practices issued interim recommendations for use. Following implementation of vaccination, cases of anaphylaxis after administration of the Pfizer-BioNTech and Moderna vaccines began to be reported. This analysis updates the reporting rates of anaphylaxis in individuals following receipt of either the Pfizer-BioNTech or Moderna vaccine. During December 14, 2020 through January 18, 2021, a total of 9 943 247 doses of the Pfizer-BioNTech vaccine and 7 581 429 doses of the Moderna vaccine were reported administered in the US (CDC unpublished data, February 2021). CDC identified 66 case reports that met Brighton Collaboration case definition criteria for anaphylaxis (levels 1, 2 or 3): 47 following Pfizer-BioNTech vaccine, for a reporting rate of 4.7 cases/million doses administered, and 19 following Moderna vaccine, for a reporting rate of 2.5 cases/million doses administered. Cases occurred after receipt of doses from multiple vaccine lots.