Real-World Evidence of Factors Associated with Respiratory Syncytial Virus Mortality in Brazilian Children Under 5 Years, 2024

Objective To investigate the clinical, demographic, and healthcare factors associated with death from Respiratory Syncytial Virus (RSV) in children under 5 years of age in Brazil during 2024. Methods Retrospective cohort study using real-world data (SIVEP-Gripe), following the RECORD protocol. A cohort of 24,022 confirmed cases was analyzed. Multivariate logistic regression was used to estimate Adjusted Odds Ratios (aOR), accompanied by sensitivity analysis (E-value) and predictive accuracy (ROC Curve). Results Hospital lethality was 1.02%. In the multivariate analysis, age was not an independent predictor of death ( p = 0.951). The main factors associated with mortality were invasive ventilatory support (aOR 8.08; 95%CI 5.28–12.38; E-value 15.64), Down Syndrome (aOR 3.21; 95%CI 1.54–6.71), Heart Disease (aOR 2.57; 95%CI 1.42–4.66), and co-infection with 3 or more viruses (aOR 2.36; 95%CI 1.16–4.79). The presence of cough showed a protective effect (aOR 0.68; p = 0.029). The model showed excellent discriminatory capacity (AUC-ROC: 0.814). Conclusion RSV mortality in hospitalized children in Brazil is driven by healthcare severity and specific comorbidities, regardless of chronological age. Immunization strategies and intensive support should prioritize biologically highly vulnerable groups, such as children with Down Syndrome and heart disease.