This retrospective cohort study used French national health data to assess whether nirsevimab immunisation (vs. no nirsevimab) reduced hospitalisation for invasive pneumococcal disease (IPD) in 527,971 liveborn children under 12 months, with 6–9 months of follow-up (birth cohort: Feb 2023–Jan 2024).
IPD occurred in 17 immunised children (14.2 per 100,000) vs. 95 non-immunised children (23.3 per 100,000). After inverse probability of treatment weighting, nirsevimab was associated with a **36% reduction** in odds of IPD at 6 months (OR 0.64, 95% CI 0.46–0.82), sustained at 9 months (OR 0.66, 95% CI 0.51–0.85).
- Only 22.6% of the cohort received nirsevimab, limiting statistical power for rare IPD events (112 total cases). - Residual confounding cannot be excluded despite propensity score weighting; immunised children may differ in unmeasured ways (e.g., healthcare-seeking behaviour, PCV uptake). - Retrospective, observational design prevents causal inference.
Nirsevimab may offer a benefit beyond RSV prevention by reducing IPD risk in infants — clinicians should be aware of this potential added value when counselling families. However, findings are observational and require confirmation before changing pneumococcal vaccination strategies.
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