Immediate side effects of Comirnaty COVID-19 vaccine: A nationwide survey of vaccinated people in Israel, December 2020 to March 2021

Background: COVID-19 vaccine safety is of major inter-est worldwide, since there is no prior experience with it. Israel was one of the first countries to widely use the Comirnaty vaccine. Aim: We aimed to assess the vaccine's short-term side effects directly from a large population and to predict influencing factors for self-reporting side effects. Methods: In a retrospective cohort study, we inves-tigated self-reported systemic vaccine side-effects using electronic surveys sent to vaccinated individuals between 20 December 2020 and 11 March 2021, within 3 days following administration of the first and second dose. We determined predictors for reporting systemic side effects by logistic regression. Results: A total of 1,213,693 patients received at least one vaccine dose and 301,537 (24.8%) answered at least one survey. Among them, 68,162 (30.4%) and 89,854 (59.9%) individuals filled the first and the second dose surveys, respectively, and reported one or more side effects. Most common side effects were fatigue, headache and myalgia. Several respondents reported facial paraesthesia after first and second dose, respectively (n = 1,675; 0.7% and n = 1,601; 1.1%). Individuals younger than 40 years and women reported side effects more frequently than others, but pregnant women reported less. Pregnancy was a weak predictor for reporting any side effect in general and in particular fatigue, myalgia, headache, chills and fever. Conclusions: We found further support for minor short-term side effects, within 3 days of receiving the Comirnaty vaccine. These findings from vaccine recipi-ents in general and pregnant women in particular can improve vaccine acceptance.