Nirsevimab Protects High-Risk Young Children in Second RSV Season
CDC real-world case-control data showed nirsevimab was 75% effective against RSV hospitalization among eligible children ages 8 to 23 months during their second RSV season. Effectiveness was higher when given within 60 days before symptoms and lower when given earlier. The study supports current recommendations for high-risk groups, including children with chronic lung disease of prematurity, severe immunocompromise, American Indian/Alaska Native children, and those with cystic fibrosis.
At IDWeek, CDC researchers presented a case-control analysis from the Overcoming RSV Network, which drew on 26 hospitals across 24 states during the 2024–2026 seasons. Among hospitalized children aged 8–23 months with respiratory symptoms, RSV was detected in 20% of nirsevimab recipients versus 42% of nonrecipients.
Adjusted effectiveness against RSV hospitalization was 75%, rising to 86% when immunization occurred within 60 days before symptoms and falling to 66% with earlier receipt. The findings support use in specified high-risk groups; prior second-season estimates have varied, including about 89% in American Indian/Alaska Native research and 42% in a small Spanish study.
The findings may reassure clinicians and families considering nirsevimab for eligible toddlers in a second RSV season, especially those with chronic lung disease, immune compromise, cystic fibrosis, or American Indian/Alaska Native children. Broader AAP indications could expand the number of children offered protection, potentially reducing hospitalizations, though effectiveness may vary by timing and population. Access, cost, and supply could influence real-world reach.