A large French cohort study reveals that nirsevimab, a long-acting monoclonal antibody used to protect against respiratory syncytial virus, is also associated with a significant reduction in hospital admissions for invasive pneumococcal disease in infants, with effects lasting up to nine months.
A large French cohort study has found that nirsevimab, the long-acting monoclonal antibody used to protect infants against respiratory syncytial virus, was also associated with fewer hospital admissions for invasive pneumococcal disease in the months after immunisation. Researchers reported that the protective association persisted for at least nine months and appeared similar across infants born at different gestational ages and birth weights.
The analysis, published in The Lancet Infectious Diseases and led by Inès Fafi of Université Paris Cité, Université Sorbonne Paris Nord and Inserm, examined more than 527,000 children born in metropolitan France between February 2023 and January 2024. About 119,000 children received nirsevimab during their first year of life, while more than 408,000 did not. Using French national health data and a weighting method to adjust for baseline differences between the groups, the investigators compared subsequent admissions for invasive pneumococcal disease, defined through hospital discharge diagnoses including meningitis, bacteraemia and severe pneumonia.
Over six months of follow-up, the incidence of invasive pneumococcal disease was 14.2 per 100,000 children in the immunised group, versus 23.3 per 100,000 among those who had not received the antibody. After adjustment, nirsevimab was linked with a 36% lower odds of hospitalisation within six months and a 34% lower odds within nine months. The researchers also reported that the association was consistent in subgroup analyses by prematurity and birth weight, while a negative control analysis did not show a relationship with invasive group B streptococcal disease, supporting the specificity of the findings.
Among the 112 pneumococcal cases recorded within six months, 20 involved meningitis and 72 involved bacteremic or complicated pneumonia. More than a third of affected children required intensive care, and all six deaths occurred in the non-immunised group. The study had limitations, including reliance on diagnostic coding, a limited nine-month follow-up period and potential uneven uptake during the first national rollout because of supply shortages. Even so, the authors said the results suggest that nirsevimab may help reduce the burden of invasive pneumococcal disease in infants alongside pneumococcal conjugate vaccination programmes.
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