Last winter’s respiratory syncytial virus (RSV) season was markedly less severe for U.S. infants, attributed in part to innovative preventive measures: a maternal vaccine and a monoclonal antibody. The 2024–25 season represented a significant milestone as these preventive measures became widely accessible. A recent study published in the Morbidity and Mortality Weekly Report highlighted that RSV hospitalization rates for infants up to 7 months were considerably lower than in past RSV seasons prior to the COVID-19 pandemic, providing a hopeful outlook on RSV management.
Historical context is essential to understanding the impacts of these preventive tools. RSV is recognized as the leading cause of hospitalizations among infants in the United States, as they lack immunity and have smaller airways susceptible to obstruction from mucus and inflammation during infections. Kawsar Talaat, a vaccine researcher at Johns Hopkins University, emphasized the severity of RSV’s effects on infants, noting that respiratory complications often lead to a full hospital wards of affected children during winter months.
The U.S. Centers for Disease Control and Prevention (CDC) now strongly recommends the use of these two preventive tools. The RSV maternal vaccine is administered as a one-time shot in the last trimester of pregnancy, generally between September and January, transferring protective antibodies to the fetus. The monoclonal antibody, nirsevimab, is designed for infants aged up to 7 months born during RSV season, offering protection that lasts for at least five months. Both strategies aim to inhibit a crucial protein the virus requires to infiltrate cells, reinforcing the defense against RSV.
Data from two surveillance networks revealed encouraging findings regarding RSV hospitalizations. The RSV-Associated Hospitalization Surveillance Network, encompassing 300 hospitals in 13 states, reported a 43 percent reduction in hospitalization rates for infants up to 7 months old during the 2024–2025 season, dropping from 15 per 1,000 children in the preceding seasons to 8.5 per 1,000. Meanwhile, the New Vaccine Surveillance Network observed a 28 percent decrease in hospitalization rates, signifying broad support for the efficacy of the new protective measures.
Remarkably, the youngest infants, particularly those under two months old, witnessed the most significant reductions in hospitalization rates, with declines of 52 and 45 percent, respectively, across the datasets. This highlights the potential for these preventive measures to drastically reduce RSV-related hospitalizations and improve infant health outcomes. Analysts envision a future where RSV-induced hospitalizations in young infants are considerably less frequent, enhancing the quality of health care provided to vulnerable populations.
However, the need for accessibility remains a prominent concern, as most RSV hospitalizations occur in regions with limited health care resources. Talaat emphasized the importance of ensuring these preventive strategies reach the most at-risk children globally, thus enhancing public health efforts and potentially improving outcomes for infants suffering from RSV in the long run.
