Background The purpose of this study was to assess whether influenza vaccination has an impact on the risk of coronavirus disease 2019 (COVID-19). Methods A cohort of 46 112 healthcare workers were tested for antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and filled in a survey on COVID-19 symptoms, hospitalization, and influenza vaccination. Results The risk ratio of hospitalization due to SARS-CoV-2 for influenza vaccinated compared with unvaccinated participants was 1.00 for the seasonal vaccination in 2019/2020 (confidence interval, .56-1.78, P = 1.00). Likewise, no clinical effect of influenza vaccination on development of antibodies against SARS-CoV-2 was found. Conclusions The present findings indicate that influenza vaccination does not affect the risk of SARS-CoV-2 infection or COVID-19.

This cohort study of 46 112 healthcare workers examined the effect of influenza vaccination on hospitalization and symptoms due to COVID-19 and development of antibodies against SARS-CoV-2. Influenza vaccination had no effect on the specified outcomes.