Bronquiolite Viral Aguda e Imunização passiva: A eficácia das novas imunizações passivas na prevenção de casos graves pelo Vírus Sincicial Respiratório

Abstract

Acute Viral Bronchiolitis (AVB), predominantly caused by Respiratory Syncytial Virus (RSV), remains the leading cause of lower respiratory tract infection and hospitalization in infants globally. In Brazil, its relevance transcends the individual clinical scope, posing a systemic challenge to the Unified Health System (SUS) due to the concentration of cases in children under one year old, the well-defined seasonality, and the significant economic impact.

This study critically analyzes contemporary evidence regarding the efficacy and effectiveness of nirsevimab—a long-lived monoclonal antibody—in preventing hospitalizations and severe outcomes related to RSV, integrating these findings into the Brazilian epidemiological and healthcare context. This is an integrative review that included Phase 3 and 3b randomized clinical trials, real-world effectiveness studies, and a national ecological analysis of seasonality, published between 2022 and 2025. The data demonstrate a reduction of over 80% in RSV hospitalizations in pragmatic contexts, in addition to consistent protection against more severe outcomes, such as the need for high-flow oxygen therapy and admission to an intensive care unit. A progressive decline in effectiveness is observed over the weeks following administration, but with maintenance of clinically relevant protection during the critical seasonal period. In light of the return to the pre-pandemic seasonal pattern and the significant hospital costs recorded in the country, the incorporation of passive immunization requires strategic time planning and regionalized cost-effectiveness analysis. Nirsevimab emerges as an intervention with structuring potential for public child health policy, capable of mitigating seasonal morbidity and rationalizing the use of hospital resources.