Effect of Influenza Vaccination on Risk of Coronavirus Disease 2019: A Prospective Cohort Study of 46 000 Healthcare Workers.

Kristensen, Jonas Henrik; Bo Hasselbalch, Rasmus; Pries-Heje, Mia; Nielsen, Pernille Brok; Dehlbæk Knudsen, Andreas; Fogh, Kamille; Boesgaard Norsk, Jakob; Eiken, Aleksander et al. · J Infect Dis · 2022

prospective_cohort · Level II

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Abstract

The purpose of this study was to assess whether influenza vaccination has an impact on the risk of coronavirus disease 2019 (COVID-19). 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. 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. The present findings indicate that influenza vaccination does not affect the risk of SARS-CoV-2 infection or COVID-19.

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