Maternal RSV vaccination to protect infants in Brazil: a model-based cost-effectiveness analysis for incorporation into the National Immunisation Program

Summary: Background: In Brazil, respiratory syncytial virus (RSV) is the primary cause of lower respiratory tract infections (LRTI) in children under two years of age. Maternal immunization with the bivalent RSV prefusion F protein vaccine (RSVpreF) has demonstrated high efficacy in protecting infants during their first 6 months of life against RSV-LRTI. We assessed the cost-effectiveness of implementing maternal RSV immunization in Brazil. Methods: We utilised a decision tree model, following a birth cohort during their first year of life. The model compared two strategies: maternal vaccination and no vaccination, from both healthcare system and societal perspectives. Secondary data from Brazilian Health Information Systems, administrative databases and international literature were used. The primary outcome was the incremental cost-effectiveness ratio (ICER) expressed as incremental cost per disability-adjusted life year (DALY) averted, in 2023 USD. We applied a cost-effectiveness threshold of 8000 USD (40, 000 BRL) per DALY based on Brazilian guidelines. Findings: Introduction of RSV vaccination for pregnant women at 50% coverage would prevent around 37, 000 RSV cases annually, including 9400 hospitalizations and 28, 000 outpatient visits. The program would avert 80 deaths and 1660 DALYs, with an incremental cost of 49, 200, 000 USD from the healthcare system perspective (ICER 29, 700 per DALY averted) and 48, 800, 000 USD from the societal perspective (ICER 29, 200 per DALY averted). These ICERs exceed the acceptable cost-effectiveness Brazilian threshold. To be considered cost-effective, the vaccine dose price would need to be around 12. In sensitivity analyses, vaccine price and efficacy were the most influential parameters, as testing their uncertainty ranges resulted in the largest changes (i. e. , the widest range) in the ICER. In the probabilistic sensitivity analysis, the probability that the maternal RSV immunization program is cost-effective at the Brazilian threshold of 8000 per DALY averted was 0% from the healthcare system perspective and 6% from the societal perspective. Interpretation: Our findings indicate maternal RSV immunization could substantially reduce disease burden but would require significant price reduction to meet Brazil's cost-effectiveness threshold. Funding: São Paulo Research Foundation (FAPESP), Pan American Health Organization (PAHO) and Brazilian National Council for Scientific and Technological Development (CNPq).