SARS-CoV-2 Reinfections in Health-Care Workers, 1 March 2020–31 January 2023

Objective: To study SARS-CoV-2 reinfections in health-care workers (HCWs) of the University Health Agency Giuliano-Isontina (ASUGI), covering provinces Trieste and Gorizia (northeastern Italy) routinely screened for via nasopharyngeal swab. Design: Cohort HCWs (N = 8205) followed since start pandemic (1 March 2020) through 31 January 2023. The risk reinfection during Omicron transmission period (after 30 November 2021) among previously infected by was estimated based on days last dose COVID-19 vaccine received, adjusting age, sex, job task, workplace, number doses vaccines swab tests performed. In crude as well adjusted incidence rate analysis, ocurring 15+ after a first or 8+ following second more were counted. Results: highly vaccinated population, entire 2020–31 2023) 5253 incurred at least one infection, 4262 only once, 1091 reinfected. Reinfections almost entirely (99.1% 1071/1091) occurred 2021, peaking July 2022 161). Six hundred eighty-three pre-Omicron primary event against 408 an event. mean 400 ± 220 infection; 512 205 event, opposed to 218 74 infection. Thirty-four hospitalizations observed, all before wave, 18 (0.4%) infections 16 (1.5%) reinfections. By excluding events occurring <15 <8 further vaccine, 605 (raw 1.4 × 1000) 404 infection 0.3 1000). Apart from nurse aids (slightly enhanced biological risk) academic (remarkably lower with events), effect occupation terms task workplace marginal. Furthermore, whilst males < 60 years old aged 30–50 likely be Regardless timeline decreased higher vaccines, being lowest booster. particular, VE 16% dose, 51% two doses, 76% booster 92% latter figures increased 72%, 59%, 74% 93%, respectively, infections. Conclusions: frequent period, though featured mild no symptoms. Whilst impact relatively marginal, vaccination had strongest protective reinfection, 93%