Nirsevimab immunization significantly lowers invasive pneumococcal disease hospitalization risk in infants, suggesting an indirect protective effect.
Real-world data show invasive pneumococcal disease (IPD) risk is significantly reduced with nirsevimab immunization among infants younger than 12 months of age, according to study results published in The Lancet Infectious Diseases
Since uptake of pneumococcal conjugate vaccines has increased worldwide, IPD is now largely caused by nonvaccine serotypes. It is hypothesized that respiratory syncytial virus (RSV) facilitates the transition to IPD
Investigators performed a population-based, retrospective cohort study sourcing data from the French National Health Data System. They aimed to determine whether nirsevimab immunization, a long-acting monoclonal antibody that targets RSV, may reduce IPD burden. Infants (N=527,971) born in metropolitan France between February 2023 and January 2024 were evaluated for hospitalization for IPD within 6 months on the basis of whether they received nirsevimab in their first year of life. To balance for cohort differences, the investigators employed an inverse probability of treatment weighting approach.
These findings should be put into perspective with a growing body of evidence suggesting interactions between RSV and S pneumoniae
Among nirsevimab recipients (n=119,435) and nonrecipients (n=408,536), 51.7% and 50.9% were boys, the median ages were 0 (IQR, 0-3) and 4 (IQR, 0-6) months, 93.7% and 95.0% were born at 37 weeks’ gestation or later, and the median birthweights were 3300 (IQR, 2980-3610) and 3300 (IQR, 3000-3610) g, respectively
During the follow-up period, fewer nirsevimab recipients were hospitalized with IPD than nonrecipients, totaling 17 infants (incidence rate [IR], 14.2 cases per 100,000) vs 95 infants (IR, 23.3 cases per 100,000)
Nirsevimab significantly reduced IPD hospitalization risk in the matched analysis (adjusted odds ratio [aOR], 0.64; 95% CI, 0.46-0.82). Similarly, nirsevimab was associated with a significant reduction in IPD hospitalization risk in all sensitivity analyses (aOR range, 0.59-0.72)
Secondary analyses revealed that nirsevimab reduced the risk for IPD hospitalization at 9 months (aOR, 0.66; 95% CI, 0.51-0.85). The investigators also noted significant risk reductions among infants with a birthweight less than 2500 g (aOR, 0.29; 95% CI, 0.11-0.74), those weighing 2500 g or higher (aOR, 0.66; 95% CI, 0.51-0.90), and those born at term (aOR, 0.65; 95% CI, 0.48-0.87). However, the reduction was not significant for infants born before 37 weeks’ gestation (aOR, 0.39; 95% CI, 0.14-1.06).
Among infants who developed IPD, nirsevimab recipients were younger at onset than nonrecipients (median, 4 vs 6 months) and had a higher rate of underlying conditions (18% vs 14%). While IPD in nirsevimab recipients was associated with a lower mortality rate (0% vs 6%), these infants experienced higher rates of intensive care unit admission (41% vs 31%) and ventilatory support (47% vs 41%)
Study limitations include nirsevimab shortages during the study period, which could have affected immunization uptake in certain regions and dates of birth
According to the investigators, “These findings should be put into perspective with a growing body of evidence suggesting interactions between RSV and S pneumoniae.”
Disclosure: Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Fafi I, Valtuille Z, Kaguelidou F, et al.Effectiveness of nirsevimab immunisation on invasive pneumococcal disease in children nationwide in France: an observational cohort study.Lancet Infect Dis. Published online July 21, 2026. doi:10.1016/S1473-3099(26)00253-7
