Fig. 2.

Adjusted prevalence proportion ratio (PPR) of HCWs who tested positive for SARS-CoV-2 infection among all cases (A) and among symptomatic cases (B) by week, with 95% Confidence Intervals (CI); and cumulative number of COVID-19 vaccine doses administered to HCW in Italy (yellow line). 1 September 2020 to 28th of March 2021. The reference was set to the week of the 03–09 November. PPR was adjusted for sex, age group (i.e., 20–34, 35–49, and 50–65 years), region of diagnosis, and regional hospitalisation rate in the previous week. Vertical black dotted line: Start of administration of the first doses of the COVID-19 vaccine (27th of december 2020). Vertical grey dotted line: Start of administration of the second doses of the COVID-19 vaccine (17th of January 2021). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)