Vaccines 2025

Respiratory Syncytial Virus (RSV) is the leading cause of hospitalization among U.S. infants, particularly those aged 0–2 months. Maternal RSV vaccination and nirsevimab (a long-acting monoclonal antibody) administration were introduced during the 2023–2024 U.S. RSV season. A study published in MMWR assessed the association between the availability of these interventions and RSV-associated hospitalizations by comparing pediatric hospitalization rates from RSV-NET and NVSN during the 2024–2025 season with those from the 2018–2020 pre–COVID-19 seasons.
The maternal RSV vaccine and nirsevimab were associated with substantial reductions in RSV-associated hospitalizations among infants aged 0–7 months during the 2024–2025 season. Specifically, the estimated relative rate reductions were 43% in RSV-NET and 28% in NVSN. The most pronounced reductions were observed among infants aged 0–2 months, the group at highest risk for severe disease. These findings suggest that these preventive strategies are highly effective in reducing severe RSV disease in the most vulnerable infant age group.
Conversely, hospitalization rates among children aged 8–19 and 20–59 months were higher during the 2024–2025 season compared to previous seasons, indicating increased overall seasonal severity and a limited impact of current prevention products in these older age groups.