Takeaways
- Nirsevimab provided the greatest overall reduction in RSV-LRTD burden, preventing more hospitalizations, emergency visits, and primary care encounters than clesrovimab or RSVpreF maternal vaccination.
- Modeled cost-effectiveness consistently favored nirsevimab, with the lowest cost per RSV-LRTD and hospitalization averted and the smallest number needed to immunize across strategies.
- Maternal RSVpreF vaccination offered more modest impact, particularly for preterm infants due to limited antibody transfer, reinforcing the need for direct infant immunization to ensure comprehensive population protection.
Findings from a newly published US modeling study report that respiratory syncytial virus (RSV) continues to generate substantial disease burden among infants, even under the historical standard of practice in which only high-risk infants received palivizumab. The model estimated 523,594 medically attended RSV lower respiratory tract disease (RSV-LRTD) events and 44,483 hospitalizations each year in infants younger than 12 months.1,2
Researchers noted that the majority of medically attended illnesses occurred in healthy late-preterm and term infants, stating that “the burden was largest among healthy infants born late preterm or term.” Infants born outside the typical RSV season from October to March accounted for 42% of hospitalizations, reaffirming the need for year-round infant protection.
How does nirsevimab perform compared with other RSV prevention options?
According to the analysis, nirsevimab—an extended half-life monoclonal antibody administered directly to infants—demonstrated the greatest projected reduction in RSV-LRTD outcomes across the whole US birth cohort.
Modeling estimated that nirsevimab would avert 364,204 RSV-LRTD cases, including 32,404 hospitalizations, 88,647 emergency department visits, and 243,103 primary care visits. Investigators reported that nirsevimab use “would have averted an estimated $1289 million in direct and indirect costs.”
Clesrovimab, another monoclonal antibody with a shorter half-life, showed variable impact depending on the assumed duration of protection. Across 100-day, 120-day, and 150-day protection scenarios, clesrovimab was estimated to prevent 173,276 to 261,358 RSV-LRTD events and 23,957 to 30,483 hospitalizations. The study highlighted uncertainty surrounding clesrovimab’s durability, noting “important questions about sustained protection throughout the 150-day RSV season.”
What is the impact of RSVpreF maternal vaccination on infant outcomes?
The study also evaluated outcomes associated with RSVpreF maternal vaccination, administered at 32 to 36 weeks of gestation. When coverage was modeled at levels equivalent to monoclonal antibody strategies, seasonal maternal vaccination prevented 76,915 RSV-LRTD events and 9649 hospitalizations, corresponding to an estimated $345 million in savings.
