BNT162b2 mRNA COVID-19 Vaccine Effectiveness in the Prevention of SARS-CoV-2 Infection and Symptomatic Disease in Five-Month Follow-Up: A Retrospective Cohort Study

Abstract

To combat the COVID-19 pandemic, a mass vaccination campaign was initiated in Italy on 27 December 2020. The vaccine available to immunize Italian healthcare workers (HCWs) was the BNT162b2 mRNA COVID-19 vaccine (Comirnaty). This study evaluated the effectiveness of the vaccine against documented SARS-CoV-2 infection and symptomatic diseases in the medium- to long-term. HCWs at Bari Policlinico University-Hospital (Italy) who completed the vaccination schedule were matched with HCWs who had refused vaccination; the two groups were followed-up for 5 months (January-May 2021). Vaccine effectiveness (VE) against infection was 97.7% (95.4-99.0%) at 14-34 days after the first dose, and 94.8% (87.0-97.8%), 83.0% (65.0-92.0%), and 81.0% (42.0-94.0%) at 14-41, 42-69, and >69 days, respectively, after the second dose. The estimated VE for documented symptomatic disease was 99.2% (96.4-99.8%) at 14-34 days after the first dose and 97.2% (90.3-99.2%), 85.0% (63.0-94.2%), and 88.0% (42.0-97.6%) at 14-41, 42-69, and >69 days, respectively, after the second dose. Efforts to increase vaccination rates should be strengthened, including mandatory vaccination for HCWs and greater incentives to increase vaccine acceptance by the general population.

Keywords: COVID-19; documented infection; healthcare workers; vaccine effectiveness.

Figure 1

Cumulative incidence of documented infection and symptomatic disease, by group (vaccinated vs. unvaccinated), expressed using Kaplan–Meier estimator.