Maintaining Safety with SARS-CoV-2 Vaccines

To the Editor: In the review article by Castells and Phillips on vaccines for the prevention of infection with SARS-CoV-2 (published on Dec. 30 at NEJM.org), 1 the authors describe cases of anaphylaxis associated with the Pfizer–BioNTech messenger RNA (mRNA) vaccine. The estimated incidence of anaphylaxis is 1 in 100,000 injections, as compared with an expected incidence of 1 in 1 million injections. 2 The incidence of anaphylaxis after vaccination with the quadrivalent human papillomavirus (HPV) vaccine (Gardasil) has been estimated at 1 in 190,000 injections 3 ; this incidence is similar to that reported for the Pfizer–BioNTech vaccine. Polysorbate 80 is an excipient . . .