TOPLINE

Nirsevimab immunization was associated with 36% lower odds of hospitalization for invasive pneumococcal disease (IPD) within 6 months of immunization and 34% lower odds of hospitalization within 9 months of immunization among infants in a nationwide French cohort.

METHODOLOGY

• Researchers conducted a population-based retrospective cohort study using data from the French National Health Data System to assess the effectiveness of nirsevimab immunization in preventing IPD among children.
• They included 527,971 children born in metropolitan France between February 2023 and January 2024, of whom 119,435 (22.6%) received nirsevimab immunization during their first year of life and 408,536 (77.4%) did not.
• A propensity score analysis using inverse probability of treatment weighting (IPTW) was conducted to balance differences in baseline characteristics; after weighting, the median age at inclusion was 3 months for the immunized group and 0-6 months for the nonimmunized group, and the sex ratio of boys to girls was 1.04 in both groups.
• The primary outcome was hospitalization for IPD within 6 months of inclusion in the study, with IPDs identified through discharge diagnoses of pneumococcal meningitis, pneumococcal bacteremia, bacteremic pneumococcal pneumonia, pneumonia with pleural effusion, and others.
• Secondary outcomes included hospitalization for IPD within 9 months of inclusion, as well as hospitalization within 6 months of inclusion in analyses stratified by prematurity status and by birth weight.

TAKEAWAY

• During the 6 months of follow-up, the incidence of IPD (per 100,000 children) was 14.2 in the immunized group and 23.3 in the nonimmunized group. After IPTW adjustment, nirsevimab immunization was associated with lower odds of hospitalization for IPD at 6 months (odds ratio [OR], 0.64; 95% CI, 0.46-0.82).
• Nirsevimab immunization remained associated with a lower risk for hospitalization for IPD at 9 months (OR, 0.66; 95% CI, 0.51-0.85), and a similar association was observed in subgroup analyses by gestational age and birth weight. A negative control outcome analysis did not show an association between nirsevimab immunization and invasive group B streptococcal disease.
• Among 112 cases of IPD that occurred up to 6 months, 20 (18%) involved meningitis and 72 (64%) involved bacteremic pneumococcal pneumonia or pneumococcal pneumonia with pleural effusion; 36 (32%) cases required ICU admission, and all six (5%) deaths occurred in the nonimmunized group.
• Pneumococcal serotype data were available for 41 (37%) of the 112 cases; serotypes 24F and 15B/C were the most common non-PCV13 serotypes involved, and serotype distribution was similar in both groups.

IN PRACTICE

“This real-world cohort study indicated that nirsevimab immunisation in children younger than 12 months of age was associated with a lower risk of IPD for at least 9 months following immunisation. Nirsevimab might help reduce the burden of IPD in children beyond PCVs [pneumococcal conjugate vaccines],” the authors of the study wrote.

SOURCE

The study was led by Inès Fafi, MD, of Université Paris Cité, Université Sorbonne Paris Nord, and Inserm, Paris, France. It was published online on July 21, 2026, in The Lancet Infectious Diseases.

LIMITATIONS

IPD cases were identified using diagnostic codes, which might have introduced some misclassification. Nirsevimab shortages during the first national immunization campaign might have led to differential uptake depending on date and region of birth. Follow-up after inclusion was limited to 9 months. Additionally, subgroup analyses by age, clinical presentation, severity, and serotype were limited by few events and should be interpreted cautiously.

DISCLOSURES

This study received support from a research fellowship from Assistance Publique-Hôpitaux de Paris; the 2023 ATIP-Avenir partnership between the National Institute for Health and Medical Research (Inserm) and the French National Centre for Scientific Research; and La Fondation de Assistance Publique-Hôpitaux de Paris. Several authors reported receiving honoraria, consulting fees, and research support and having other ties with various sources, including GSK, Sanofi, Pfizer, and others. Full disclosures are noted in the original article.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.