Effectiveness of AstraZeneca vaccine against SARS-CoV-2 (ChAdox1-S) in reducing in-hospital mortality in individuals with COVID-19 and schizophrenia: A retrospective cohort study

Abstract

ChAdOx1-S is a viral vector vaccine developed by AstraZeneca. We aimed to assess the effectiveness of 1 and 2 doses of the ChAdOx1-S vaccine in reducing COVID-19-related in-hospital mortality in individuals with schizophrenia. This is a retrospective cohort study using a nationwide hospital database in Brazil. Individuals diagnosed with COVID-19 and schizophrenia were included in the study. The exposures were 0, 1, and 2 doses of ChAdOx1-S. The outcome of mortality was measured in hazard ratios (HR), calculated using multivariable Cox regression models. The study included 1,929 positive cases of COVID-19 in schizophrenia patients. After adjusting for age, socioeconomic factors, and comorbidities, we observed a significant 55% decrease in the hazard of mortality in the 2-dose vaccination group (HR 0.45, 95% CI: 0.310–0.652) compared to the unvaccinated. Surprisingly, our results did not show any significant reduction in the hazard of mortality in the 1 dose vaccination group (HR 1.278, 95% CI: 0.910–1.795). The effectiveness of two doses of ChAdOx1-S in individuals with schizophrenia aligns with findings from studies on the general population. That one dose was insignificant. Overall, these findings are important for informing public health decisions–prioritizing individuals with schizophrenia for vaccinations and managing acceptance of vaccines.