The Prevalence of Immediate Hypersensitivity Reactions to the BNT162b2 mRNA Vaccine against SARS-CoV-2: Data from the Vaccination Campaign in a Large Academic Hospital

: The anti-SARS-CoV-2 vaccination has probably been the most effective tool for preventing the infection and negative outcomes of the COVID-19 disease, and therefore for interrupting the pandemic state. The first licensed SARS-CoV-2 vaccine was BNT162b2, an mRNA vaccine that has been widely used since the earliest stages of the global vaccination campaign. Since the beginning of the vaccination campaign, some cases of suspected allergic reactions to BNT162b2 have been described. Epidemiological data, however, have provided reassuring results of an extremely low prevalence of these hypersensitivity reactions to anti-SARS-CoV-2 vaccines. In this article, we describe the results of a survey carried out through the use of a questionnaire, administered to all the health personnel of our university hospital after the first two doses of the BNT162b2 vaccine, which investigated the development of adverse reactions after a vaccination. We analyzed the responses of 3112 subjects subjected to the first dose of the vaccine; among these, 1.8% developed symptoms compatible with allergic reactions and 0.9% with clinical manifestations of possible anaphylaxis. Only 10.3% of the subjects who had allergic reactions after the first injection experienced similar reactions after the second dose and none of them experienced anaphylaxis. In conclusion, the anti-SARS-CoV-2 vaccination is rarely associated with severe allergic reactions and the second dose of vaccine is safe for this group of patients.