NEW YORK: Hospitalisation rates for infants with respiratory syncytial virus (RSV) fell significantly during the 2024–2025 season compared to pre-COVID levels, according to new data published in the Morbidity and Mortality Weekly Report (MMWR) by the US Centers for Disease Control and Prevention (CDC).
Surveillance data from the RSV-Associated Hospitalisation Surveillance Network (RSV-NET) and the New Vaccine Surveillance Network (NVSN) revealed that RSV-associated hospitalisations among infants aged 0 to 7 months declined by 43% and 28%, respectively, when compared to pooled data from the 2018–2020 RSV seasons.
The findings coincide with the widespread use of two major preventive tools introduced in 2023: Pfizer’s maternal RSV vaccine Abrysvo and the monoclonal antibody nirsevimab (Beyfortus), developed by Sanofi and AstraZeneca.
These tools were available throughout the 2024–2025 RSV season and contributed significantly to the drop in infant hospitalisations.
“These findings support the Advisory Committee on Immunization Practices’ recommendations for maternal vaccination or nirsevimab to protect against severe RSV disease in infants,” the MMWR study authors noted.
They stressed the importance of administering preventive interventions early in the RSV season, ideally during the birth hospitalisation for infants born during peak transmission months.
The most pronounced reductions were observed among infants aged 0 to 2 months during the December–February peak period.
In this age group, RSV-NET data showed a 52% reduction in hospitalisation rates (95% confidence interval: 49%–56%), while NVSN recorded a 45% reduction (95% CI: 32%–57%).
A separate January 2025 study in JAMA Network Open highlighted the real-world effectiveness of these preventive tools.
The study found that 64% of eligible pregnant individuals received the RSV vaccine and 70.1% of eligible infants were administered nirsevimab, resulting in over 80% protection against RSV during much of the RSV season.
Further supporting evidence was published in The Lancet on 1 May 2025, offering the first pooled analysis of nirsevimab’s effectiveness outside clinical trials.
The data, drawn from observational studies in five countries, confirmed high efficacy in preventing RSV-related complications in infants.
Additional insights from a Pediatrics study showed that 72% of infants were immunised against RSV, based on health records from 36,949 infants born across 43,722 pregnancies in ten Vaccine Safety Datalink health systems.
