Vaccines may induce positive non-specific immune responses to other pathogens This study aims to evaluate if influenza vaccination in the 2019&ndash;2020 season had any effect on the risk of SARS-CoV-2 confirmed infection in a cohort of health workers During the first SARS-CoV-2 epidemic wave in Spain, between March and May 2020, a cohort of 11,201 health workers was highly tested by RT-qPCR and/or rapid antibody test when the infection was suspected Later in June, 8665 of them were tested for total antibodies in serum A total of 890 (7 9%) health workers were laboratory-confirmed for SARS-CoV-2 infection by any type of test, while no case of influenza was detected The adjusted odds ratio between 2019&ndash;2020 influenza vaccination and SARS-CoV-2 confirmed infection was the same (1 07;95% CI, 0 92&ndash;1 24) in both comparisons of positive testers with all others (cohort design) and with negative testers (test-negative design) Among symptomatic patients tested by RT-qPCR, the comparison of positive cases and negative controls showed an adjusted odds ratio of 0 86 (95% CI, 0 68&ndash;1 08) These results suggest that influenza vaccination does not significantly modify the risk of SARS-CoV-2 infection The development of specific vaccines against SARS-CoV-2 is urgent
Influenza Vaccination and Risk of SARS-CoV-2 Infection in a Cohort of Health Workers