by mid-January, 2021. The Sheba Medical Centre, Israel's largest hospital with 9647 HCWs,
began staff vaccination on Dec 19, 2020. All HCWs, excluding those with previous SARS-
CoV-2 infection, were eligible for vaccination. Clinical trial data of BNT162b2 vaccine
estimated an early vaccine efficacy in preventing COVID-19 of 52· 4% before dose two, and
90.5% on days 2–7 after dose two.