COVID-19 Seropositive Rates between the Waves, Israel.

Background: Israel has experienced three waves of coronavirus disease-2019 (COVID-19) infection since late February 2020, with lockdown and other measures employed to contain infection rates. In cooperation with the Israel Ministry of Health, serological testing was conducted by all four health maintenance organizations (HMO) in order to estimate national infection rates and the proportion of previously undetected disease.

Objectives: To estimate the proportion of the population that was seropositive, identify factors associated with seropositive outcome, and approximate the proportion of residents that were asymptomatic.