COVID-19 vaccine effectiveness against in-hospital mortality in immunocompromised older adults: a Brazilian hospital surveillance study, 2024.

OBJECTIVE: The study evaluated the association between COVID-19 vaccination and in-hospital mortality among immunocompromised older adults hospitalized for COVID-19 in Brazil during the 2024 epidemiologic year. METHODS: This retrospective hospital-based surveillance study used data from the Brazilian SIVEP-Gripe database. All hospitalized cases of COVID-19-related severe acute respiratory syndrome in immunocompromised individuals aged ≥60 years reported during epidemiological weeks 1-52 of 2024 were included. Multivariable logistic regression was used to estimate odds ratio (OR) and 95% confidence interval (95%CI) for the association between COVID-19 vaccination (number of doses) and in-hospital mortality, adjusting for clinical and sociodemographic covariates. RESULTS: Among 474 patients, in-hospital mortality was 36% (171/474). Only 56 (12%) were unvaccinated. Compared with unvaccinated individuals, adjusted ORs for mortality were 0.67 (95%CI 0.32-1.39) for 1-2 doses, 0.67 (95%CI 0.31-1.42) for 3 doses, 0.54 (95%CI 0.26-1.15) for 4 doses, and 0.56 (95%CI 0.26-1.17) for 5-6 doses. Mechanical ventilation (OR 12.55; 95%CI 6.39-26.33) and lower educational attainment (elementary education: OR 2.94; 95%CI 1.39-6.44) were independent predictors of death. COVID-19 vaccination was not significantly associated with reduced in-hospital mortality among immunocompromised older adults hospitalized for the disease in Brazil in 2024. However, all adjusted ORs were below unity, suggesting a trend toward protection with increasing doses. CONCLUSIONS: The strong association of mortality with mechanical ventilation and social determinants highlights the need for timely boosters and comprehensive preventive strategies for this vulnerable population.