Although clinical trials for approved COVID-19 vaccines demonstrated efficacy of the vaccine in preventing symptomatic infection, many questions about vaccine effectiveness, such as the effectiveness of COVID-19 vaccine in preventing asymptomatic infection, a surrogate for transmission, and duration of protection, can only be evaluated in real-world trials. The objective of the study is to evaluate COVID-19 vaccine effectiveness (Pfizer vaccine, and, if available, Moderna vaccine) in preventing infection in healthcare personnel in Israel. HCP who are Clalit members and working in Soroka, Beilinson, Meir, Haemek, Kaplan and Schneider hospitals, 18 years or older, and eligible to get COVID-19 vaccine according to Ministry of Health guidelines, will be recruited, regardless of their intention to get the COVID-19 vaccine. A baseline serology sample and respiratory sample will be collected. Participants will be asked to provide a respiratory sample weekly for 3 months, and then monthly for the remainder of the study. Participants will also have blood drawn at 1 month, 3 months, 6 months, 9 months and 12 months. Respiratory samples will be tested for SARS-CoV-2 by RT-PCR; serology will be tested for SARS-CoV-2 antibodies. The study will last for 12 months. For each participant, data will be extracted from the Electronic Medical Record for the period of the study and retrospectively from 2010.

Inclusion Criteria:

- Any HCP at any of the participating hospitals who is

• a member of Clalit Health Services
• is eligible to get the Covid-19 vaccine
• did not receive the first dose of COVID-19 vaccine more than 21 days prior to the enrollment date

Exclusion Criteria:

-

Employees at any of the participating hospitals will be excluded if they are:

• not a member of Clalit Health Services; or
• not eligible to get the Covid-19 vaccine according to the Ministry of Health guidelines; or
• Less than 18 years of age
• Received first dose of COVID-19 vaccine more than 21 days prior to date of enrollment

Healthcare workers who work in 6 Clalit hospitals in Israel (Soroka, Kaplan, Meir, Beilinson, HaEmek, and Schneider)