Impact of Universal Varicella Vaccination in Israel: A Time-Series Analysis, 2003 to 2020

Background: Two-dose universal varicella vaccination (UVV) was included in Israel's national immunization program in 2008. We aimed to evaluate the impact of the UVV program on varicella incidence and healthcare costs in Israel. Methods: A retrospective observational study was conducted using the Maccabi Healthcare Services database between 2003 and 2020. Varicella incidence and varicella-related healthcare costs were assessed in the pre- (2003-2007) and post-UVV (2010-2020) periods. We used time-series analyses with seasonal autoregressive integrated moving average models to estimate the impact of UVV on varicella incidence and regression models with gamma distributions and log-link functions to assess the impact on healthcare costs. Analyses were conducted for the overall population and vaccine-targeted (1-7 years) and nontargeted (<1 and >7 years) populations. Results: Annual incidence rates per 100,000 declined from 5709.6 (pre-UVV) to 1062.9 (post-UVV) in the vaccine-targeted population and from 1269.8 to 409.6 in the overall population. Time-series analysis suggested 81.8% (95% prediction interval [PI], 67.5-87.4) and 67.1% (95% PI, 48.2-75.9) reductions in the vaccine-targeted vaccination and overall populations, respectively. The largest estimated reduction in varicella incidence was in children 1 to 2 years of age [91.2% (95% PI, 53.4-95.3)]. Mean direct medical costs decreased between pre- and post-UVV periods by 82% (95% confidence interval, 77-86) in the vaccine-targeted group and 51% (95% confidence interval, 44-58) overall. Conclusions: This real-world study demonstrates the substantial reduction in the disease and economic burden of varicella in the vaccine-targeted and overall population following the introduction of a 2-dose UVV program in Israel.