Incidence of COVID-19 Infection in Hospital Workers From March 1, 2020 to May 31, 2021 Routinely Tested, Before and After Vaccination With BNT162B2

Objective: To evaluate the incidence of COVID-19 infection in health care workers from the start of COVID-19 pandemic in NE of Italy, to the vaccination with BNT162b2. Materials and methods This was a retrospective cohort study. Health care workers were routinely tested for SARS-CoV-2 infections using real-time polymerase chain reaction tests in nasopharyngeal swabs. Logistic regression was used to calculate incident rate ratios (IRRs) of factors associated to COVID-19. Results A total of 4251 workers were followed-up and an annual incidence of COVID-19 of 13.6% was found. In March 2021 the incidence of infection was 4.88 and 103.55 cases for 100.000 person-days in vaccinated and non-vaccinated workers, respectively, with an adjusted IRRs of 0.05 (95% CI 0.02–0.08). Conclusions Our study evaluated the monthly incidence in health care workers in Trieste hospitals before and after the vaccination finding the protective effect of BNT162B2 vaccine in 95% of health care workers routinely tested.