COVID-19 Booster Vaccination among Individuals with Schizophrenia in Israel

Importance: Individuals with schizophrenia are at higher risk for severe COVID-19 illness and mortality. Previous reports have demonstrated vaccination gaps among this high-risk population; however, it is unclear whether these gaps have continued to manifest with the booster dose. Objective: To assess gaps in first, second, and booster vaccinations among individuals with schizophrenia. Design, Setting, and Participants: This was a matched, controlled, retrospective cohort study conducted in November 2021, and included follow-up data from March 2020, to November 2021. The study used the databases of Clalit Health Services, the largest health care management organization in Israel. Individuals with a diagnosis of schizophrenia at the onset of the pandemic and matched controls were included in the analysis. Main Outcomes and Measures: Rates of first, second, and booster vaccinations and time to reach vaccination. Results: The study included 34797 individuals (mean [SD] age, 50.8 [16.4] years; 20851 men [59.9%]) with schizophrenia and 34797 matched controls (mean [SD] age, 50.7 [16.4] years; 20851 men [59.9]) for a total of 69594 individuals. A total of 6845 of 33045 individuals (20.7%) with schizophrenia were completely unvaccinated, compared with 4986 of 34366 (14.5%) in the control group (odds ratio [OR], 0.65; 95% CI, 0.62-0.67, P <.001). Once vaccinated, no significant differences were observed in the uptake of the second vaccine. Gaps emerged again with the booster vaccine, with 18469 individuals (74.7%) with schizophrenia completing the booster, compared with 21563 (77.9%) in the control group (OR, 0.83; 95% CI, 0.80-0.87, P <.001). Kaplan-Meier analyses indicated significant differences in time to reach vaccination, although gaps were lower compared with those reported in the first vaccination (log-rank test, 601.99 days; P <.001 for the first vaccination, compared with log-rank test, 81.48 days, P <.001 for the booster). Multivariate Cox regression analyses indicated that gaps in the first and booster vaccine were sustained even after controlling for demographic and clinical variables (first vaccine: hazard ratio [HR], 0.80; 95% CI, 0.78-0.81; P <.001 and booster: HR, 0.88; 95% CI, 0.87-0.90; P <.001) but were not significant for the second vaccine. Conclusions and Relevance: Results of this cohort study of Israeli adults found lower rates of COVID-19 vaccination among individuals with schizophrenia compared with a control group without schizophrenia, especially during the vaccine initiation phase. Countries worldwide should adopt strategies to mitigate the persistence of vaccination gaps to improve health care for this vulnerable population..