RSV Prevention Overview: Maternal Vaccines and Monoclonal Antibodies

This episode offers a structured overview of the prevention options now available for RSV. Dr. Simões outlines three main strategies: maternal immunization, and two long-acting monoclonal antibodies. Maternal immunization is recommended in the U.S. between 32 and 36 weeks of completed gestation, with at least 14 days needed between vaccination and delivery to allow maximum transplacental antibody transfer. The U.S. is divided into regional zones with individualized seasonality recommendations, reflecting the heterogeneity highlighted earlier in the series.

For infants who miss the protection conferred through maternal vaccination, Dr. Simões describes the two approved monoclonal antibodies in detail. Nirsevimab was licensed for the 2023–2024 season and can be used across two RSV seasons; it is weight-dosed (50 mg for infants under 5 kg, 100 mg for infants over 5 kg). The second monoclonal antibody, clesrovimab, is administered as a single 105 mg dose regardless of weight and has recently received licensure in the U.S. and expanded approval in Europe. Both monoclonals are most effective when administered as a birth dose — the optimal window when 98% of births occur in hospitals — but can be given at subsequent well-child visits as well.

Dr. Simões also underscores that 80% of all RSV hospitalizations are in full-term babies under 6 months, reinforcing that prophylaxis should not be reserved only for high-risk infants. He notes that Down syndrome represents a gap in current coverage, as this population is not yet addressed by available preventive strategies. For high-risk children entering a second RSV season, both modalities remain applicable, and emerging data support their continued use.

In the next episode, "RSV Monoclonal Antibodies: Mechanisms of Action and How to Explain Them to Families," panelists unpack the science behind long-acting monoclonal antibodies and offers practical language for clinicians communicating with parents.