The COVID-19 Trajectory in Israel: A Comprehensive Analysis of National Surveillance Data on Documented Infections, Test Positivity, and Vaccine-Effectiveness Estimates
TL;DR
Within the domain of documented infection, the early vaccination-associated advantage attenuated substantially within months and was further reduced when prior-infection history and vaccination-stratified testing were incorporated; in the latter analysis, the contrast reversed by late 2021 and remained negative thereafter.
Abstract
Background: Israel was among the first countries to implement rapid nationwide BNT162b2 vaccination and became a major source of early real-world evidence on COVID-19 vaccine effectiveness. Early Israeli studies reported approximately 90-95% effectiveness against documented SARS-CoV-2 infection, but over relatively short epidemiological periods. This study examines the national trajectory from the pre-vaccination period through the end of the global COVID-19 emergency. Methods: Five publicly available Israeli Ministry of Health surveillance datasets were analyzed longitudinally from February 2020 through May 2023. National trajectories of documented infection and test positivity were characterized before and after vaccine rollout, which began on December 20, 2020. Vaccinated-unvaccinated differences were then examined in two ways: first, using routine-surveillance case rates by vaccination status; and second, using an age-adjusted test-positivity analysis among individuals without documented prior infection, with testing denominators stratified by vaccination status. The second analysis, designed to address potential biases from prior-infection history and differential testing, began 19 weeks later, when the required data became available on May 30, 2021. Results: The two completed pre-rollout waves declined to [≤]10% of their peaks within 32 and 43 days, respectively. The winter 2020-2021 wave, which was already underway when vaccination began, required 68 days. Subsequent major peaks were larger than the January 2021 peak, with Delta 17% higher and Omicron approximately nine times higher. Routine surveillance reached an early apparent vaccine-effectiveness peak of 94.4% in mid-February 2021 and declined to 61.5% by late May, with substantial rebounds thereafter. By early December it was 79.9%, before falling to 37.4% two weeks later and 8.2% by late December; it became persistently negative in February 2022. The test-positivity analysis showed a generally lower trajectory. After unstable estimates during the low-incidence summer weeks, it reached 62.1% in early December, fell to 26.8% one week later and -14.5% the next, and remained negative thereafter. Conclusions: These observational data cannot establish causal vaccine effects and do not address protection against hospitalization, severe disease, or death. Within the domain of documented infection, however, the early vaccination-associated advantage attenuated substantially within months and was further reduced when prior-infection history and vaccination-stratified testing were incorporated; in the latter analysis, the contrast reversed by late 2021 and remained negative thereafter. At the population level, national surveillance showed no sustained reduction in the magnitude or resolution of documented-infection waves after rollout. The Israeli experience may therefore be informative for future public-health emergencies, in which early short-window effectiveness estimates may change substantially as population immunity, testing practices, and the pathogen itself evolve.