The association of vaccination and the incidence of new cases of COVID-19 among health care workers, December 16, 2020 through May 4, 2021

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes the coronavirus disease 2019 (COVID-19). This highly transmissible and pathogenic virus has caused a significant threat to health care workers (HCW) as well as human health and public safety. Several studies have shown the value and effectiveness of messenger ribonucleic acid (mRNA) vaccines (mRNA) protecting HCWs from symptomatic or asymptomatic SARS-CoV-2 infections. New research is needed to demonstrate the effectiveness of vaccines where the follow-up periods are more extended than prior research. This study uses a "real-world" cohort of HCWs and provides insight into the effectiveness of the mRNA vaccines against HCWs with symptomatic SARS-CoV-2 infection. Symptomatic SARS-CoV-2 infection occurred in 5 fully vaccinated HCWs and 124 unvaccinated HCWs (incidence rate, 4.14 vs. 95.53 per 100 000 person-days, respectively, incidence risk ratio (IRR), 0.0433 [95% CI, 0.018-0.1]). Receipt of the authorized mRNA vaccines was associated with a significantly lower incidence of symptomatic SARS-CoV-2 infection for a median follow-up of 139 days. Ways to enhance complete vaccination and, subsequently, optimal immunity is required to lift masking restrictions in the health care settings.