Nirsevimab: A Turning Point in RSV Prophylaxis for Infants

Respiratory syncytial virus continues to drive significant morbidity in infants, yet prevention efforts have lagged behind advances in treatment, leaving a critical window of vulnerability in the youngest patients.

For pediatric infectious disease specialists, the advent of long-acting monoclonal antibodies marks a turning point. A pivotal phase 3 trial demonstrated that Nirsevimab reduced medically attended RSV lower respiratory tract infection by 74.5% in infants during their first RSV season, as detailed in a study on nirsevimab's efficacy. Those findings challenge previous assumptions about the feasibility of single-dose, season-long prophylaxis in neonates and young infants.

Real-world observational data corroborate these findings, though differences in study populations and settings may affect observed effectiveness. A CDC report on Nirsevimab reported a 90% reduction in RSV-related hospitalizations (95% CI: 82%–95%) among infants who received the antibody compared with those who did not, based on observational data across multiple U.S. states, acknowledging potential confounding inherent in non-randomized studies.

Complementary strategies are emerging alongside direct antibody administration. A comprehensive narrative review on RSV prevention illustrates that maternal immunization induces transplacental antibody transfer, bridging protection until infants can receive Nirsevimab. Such dual-layered approaches may be particularly valuable for preterm or medically complex infants whose passive immunity wanes sooner.

Incorporating these innovations into clinical pathways will require coordinated scheduling of prenatal vaccination per ACIP recommendations, timely dosing of Nirsevimab in neonatal clinics, and monitoring of antibody persistence. Ongoing surveillance of RSV strain variability and longer-term follow-up studies will refine dosing intervals and determine whether repeat dosing in subsequent seasons confers additional benefit. Equitable access remains paramount to ensure that all high-risk infants benefit from both maternal and direct antibody prophylaxis.

Key Takeaways:

• Nirsevimab reduces medically attended RSV LRTI by 74.5% in clinical trials.
• Implementation data show a 90% decrease in RSV-related hospital admissions among treated infants.
• Maternal vaccination provides passive immunity that complements direct monoclonal antibody prophylaxis.
• Integrated care models and equitable distribution are essential to maximize impact on infant respiratory health.