Respiratory syncytial virus (RSV) is the leading cause of hospitalization among infants in the United States.
Recent findings of the impact of new RSV prevention products aimed at protecting babies were published in the Morbidity and Mortality Weekly Report, an epidemiological digest prepared by the Centers for Disease Control and Prevention.
“The introduction of a maternal RSV vaccination and the infant monoclonal antibody, nirsevimab, is associated with meaningful reductions in infant hospitalizations,” said Natasha Halasa, MD, MPH, Craig-Weaver Professor of Pediatrics at Monroe Carell Jr. Children’s Hospital at Vanderbilt. “For decades no effective preventive options existed, and we finally have tools to prevent severe disease.
“The goal of the study was to compare RSV-associated hospitalization rates in the 2024-2025 season with pre-COVID seasons (2018-2020) to see if these products made a difference — they did,” said Halasa, one of the study investigators.
What the teams found:
- Among infants 0-7 months old, hospitalization rates dropped significantly.
- The biggest decline was in infants 0-2 months old, up to 52% reduction.
- The decrease was most pronounced during peak RSV months (December-February).
“Interim Evaluation of Respiratory Syncytial Virus Hospitalization Rates Among Infants and Young Children After Introduction of Respiratory Syncytial Virus Prevention Products — United States, October 2024–February 2025” was published this week.
Investigators compared pediatric RSV-associated hospitalization rates from two U.S. active surveillance systems, the RSV-Associated Hospitalization Surveillance Network (RSV-NET) and the New Vaccine Surveillance Network (NVSN).
RSV-NET conducts active population-based surveillance for laboratory-confirmed RSV-associated hospitalizations identified through clinical testing among catchment-area residents of all ages in more than 300 hospitals in 161 counties across 13 states. NVSN conducts active, population-based surveillance for acute respiratory illness among hospitalized children less than 18 years old at seven U.S. medical centers. Respiratory specimens from all enrolled children are tested for RSV.
Public health interest in respiratory viruses is at an all-time high, said Halasa.
The first vaccines and monoclonal antibodies for RSV were approved by the Food and Drug Administration in May 2023 and became widely available during the 2024-2025 respiratory virus season. The CDC recommends early immunization with nirsevimab for all infants less than 8 months old to protect them from severe RSV. Pregnant women should receive the maternal RSV vaccine between 32 and 36 weeks of pregnancy, according to CDC guidelines.
The report urges medical professionals and parents to continue to discuss RSV and the recommendations to help in prevention efforts.
“Full effectiveness hinges on timely delivery — during pregnancy and right after birth,” said Halasa. “The findings from this study indicates that we are on the right path in reducing the risk of RSV hospitalizations in infants.”
