COVID-19 Booster Vaccination Among Individuals With Schizophrenia in Israel

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.

To assess gaps in first, second, and booster vaccinations among individuals with schizophrenia.

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.

Rates of first, second, and booster vaccinations and time to reach vaccination.

The study included 34 797 individuals (mean [SD] age, 50.8 [16.4] years; 20 851 men [59.9%]) with schizophrenia and 34 797 matched controls (mean [SD] age, 50.7 [16.4] years; 20 851 men [59.9]) for a total of 69 594 individuals. A total of 6845 of 33 045 individuals (20.7%) with schizophrenia were completely unvaccinated, compared with 4986 of 34 366 (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 18 469 individuals (74.7%) with schizophrenia completing the booster, compared with 21 563 (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.

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.