Statistical analysis:
The main outcomes were the incidence of new SARS-CoV-2 infection in HCWs before and after vaccination, and the vaccine effectiveness (VE) against any SARS-CoV-2 infection. The outcomes were analysed for predefined subgroups according to age, gender, profession, workplace, and vaccination status. Data were presented as a median with interquartile range (IQR) of continuous variables and proportions of dichotomous variables. Univariable and multivariable logistic regression models were used to assess factors associated with the primary outcomes of SARS-CoV-2 infection. Details on statistical analysis including sample size calculations are presented in the Supplementary Material . Statistical analyses were performed using the Statistica data analysis software system (TIBCO Software Inc.), version 13. Two-side tests with a p-value of < 0.05 were considered statistically significant.