COVID-19 Vaccination, Morbidity, and Mortality During a 12-Month Period in Israel: Can We Maintain a "Herd Immunity" State?

Despite widespread vaccination, the COVID-19 pandemic continues to cause global disruption. Authors describe the pace of COVID-19 vaccination in Israel and examine differences in morbidity and mortality rates over time between vaccinated and unvaccinated populations. Retrospective data were obtained between December 2020 and December 2021 on daily vaccine uptake by age group (20-39, 40-59, 60+ years): rate of hospitalized severely ill cases, vaccination status and age group, and death rate per 100,000 by date and vaccination status. Uptake of first and second doses was slower in 20-59-year olds, whereas in 60+-year olds, it occurred without delay. Once most adults were vaccinated, a gap appeared with much higher severe cases and deaths in unvaccinated versus vaccinated populations; this gap attenuated by late May with very low rates in both vaccinated and unvaccinated populations until mid-July, when rates began to rise again. A herd-immunity-like period occurred in Spring 2021, with unvaccinated benefitting from a highly vaccinated population. Staggered vaccine uptake led to unsynchronized high immunity, which contributed to the fourth pandemic wave. Population vaccination within a shorter timeframe or shorter intervals between boosters may be important to reduce viral transmission.