Host factors and history of SARS-CoV-2 infection impact the reactogenicity of BNT162b2 mRNA vaccine: results from a cross-sectional survey on 7,014 workers in healthcare.

OBJECTIVE

This study aimed to improve the post-marketing surveillance on mRNA anti-SARS-CoV-2 vaccines, characterizing the adverse events (AEs) after the first dose of mRNA BNT162b vaccine. The associations between the AEs and individuals' characteristics were explored.

PATIENTS AND METHODS

All adult healthcare workers at Niguarda Hospital (Milan, Italy) who were referred for the first dose of vaccine were offered to participate in a cross-sectional survey during the second-dose administration, between 18 January and 7 February 2021. All participants completed a questionnaire about age, gender, weight, height, medical history, concurrent therapies, employment status, previous diagnosis/testing for SARS-CoV-2 infection, and a list of 24 AEs (solicited AEs). The development of at least one solicited AEs was the main outcome. AEs were stratified by the presence of injection-site symptoms, systemic symptoms or both, and the differences between strata were assessed as a secondary outcome. Biometric data and reports of a previous diagnosis of SARS-CoV-2 infection were also explored, as predictors of the main outcome.

RESULTS

7,014 healthcare workers were included. An incidence of 3 per 10.000 persons for serious AEs following the first administration of the mRNA BNT162b vaccine was found. An association between the development of non-serious AEs with young age, female gender, low body mass index, and previous history of SARS-CoV-2 was described.

CONCLUSIONS

This real-life study supported data on the safety profile of the BNT162b2 mRNA vaccine. Our findings on the associations between the development of non-serious AEs with some individual characteristics may help physicians and patients make educated and informed medical decisions towards anti-COVID-19 vaccination.