Clin Microbiol Infect. 2021 Jun 28:S1198-743X(21)00347-5. doi: 10.1016/j.cmi.2021.06.026. Online ahead of print.
OBJECTIVES: To evaluate the effect of mRNA SARS-Cov-2 vaccination on the incidence of new SARS-CoV-2 infections in health care workers (HCW).
METHODS: The evolution of the incident rate of microbiologically confirmed SARS-CoV-2 infection in a cohort of 2590 HCW after BNT162b2 mRNA SARS-CoV-2 vaccination, as compared to the rate in the community (n=170513) was evaluated by mixed Poisson regression models.
RESULTS: A total of 1820 HCW (70,3% of total) received the first dose of the BNT162b2 mRNA vaccine between January 10-16, 2021), and 296 (11,4%) the following week. All of them completed vaccination 3 weeks later. Incidence rates of SARS-CoV-2 infection after the first dose of mRNA SARS-CoV-2 vaccine declined by 71% (Incidence Rate Ratio (IRR) 0.286, 95% confidence interval (CI) 0.174-0.468, p< 0.001) and by 97% (IRR 0.03 95% CI 0.013-0.068, p<0.001) after the second dose as compared to the perivaccine time. SARS-CoV-2 incidence rates in the community (with a negligible vaccination rate) had a much lower decline: 2% (IRR 0.984; 95% CI 0.943-1.028; p = 0.47) and 61% (IRR 0.390, 95% CI 0.375-0.406; p<.001) for equivalent periods. Adjusting for the decline in the community, the reduction in the incident rates among HCW were 73% (IRR 0.272; 95% CI 0.164-0.451 p<0.001) after the first dose of the vaccine and 92 % (IRR 0.176, 95% CI 0.033-0.174; p<0.001) after the second dose.
CONCLUSIONS: mRNA SARS-CoV-2 vaccination is associated with a dramatic decline in new SARS-CoV-2 infection among HCW, even before the administration of the second dose of the vaccine.