Reactogenicity of a third BNT162b2 mRNA COVID-19 vaccine among immunocompromised individuals and seniors - A nationwide survey

Background: Since July 13, 2021, a third SARS-CoV-2 vaccine BNT162b2 was approved in Israel to immunocompromised and seniors 60 years of age or older. We aimed to evaluate vaccine's reactogenicity. Methods: A retrospective cohort, using electronic surveys sent to booster vaccine recipients, during July 20–August 10, 2021. Results: 17,820 participated in the survey, with a response rate of 30.2%. 3195 (17.9%) were immunocompromised. Fatigue, myalgia and fever were the most frequent systemic side effects reported (19.6%, 9.2% and 8.1% respectively among immunocompromised; 21.3%, 9.9% and 9.2% respectively among seniors). 67.3% of immunocompromised and 62% of seniors reported experiencing a better or a similar response to the third dose, compared to the second. Conclusions: Local and systemic reactions after third BNT162b2 vaccine, reported by immunocompromised and seniors, were similar to those observed following previous vaccines and mostly self-resolved. These findings may aid promoting confidence among vaccine providers and recipients.