Evidence on Nirsevimab: Sustained Impact Across Two RSV Seasons

Impact of universal nirsevimab prophylaxis in infants on hospital and primary care outcomes across two respiratory syncytial virus seasons in Galicia, Spain: A population-based prospective observational study

Study Objective

The objective of this publication was to assess the medium-term impact of universal infant RSV prophylaxis with nirsevimab across inpatient and outpatient settings during two consecutive RSV seasons

Results:
Impact on Key Hospitalization Outcomes

Universal infant nirsevimab prophylaxis was associated with substantial reductions in RSV-related hospitalizations with sustained reductions in RSV-related LRTI hospitalizations into the second season

Additional outcome including pneumonia, was also analyzed (refer manuscript for full results).
CI, Confidence Interval; LRTI, Lower Respiratory Tract Infection; RSV, Respiratory Syncytial Virus.

Results:
RSV-Related LRTI Hospitalization Over Time

As illustrated in the graph above:

Immediate and substantial reduction in RSV burden: During the first RSV season, observed hospitalizations remain near zero compared to the high expected peak.
Sustained protection into the second RSV season: The gap between expected and observed hospitalizations persists into the second season, demonstrating a carry-over effect beyond the initial season of protection.
No evidence of rebound: The second-season data does not show an increase above expected levels, supporting no shift toward delayed or more severe disease.

Adapted from Razzini J L, et al. Available at: https://doi.org/10.1016/S1473-3099(25)00742-X.
Observed (green) and expected (blue) weekly RSV-related LRTI hospitalizations with 95% CIs (shaded bands) across first RSV season, second RSV season, and up to 18 months follow-up. Expected counts assume no immunization for the 2023-24 cohort.
CI, Confidence interval; LRTI, Lower Respiratory Tract Infection; RSV, Respiratory Syncytial Virus.