TOPLINE

Among infants younger than 12 months in Finland, the implementation of a nationwide nirsevimab immunisation programme was associated with reductions in the incidence of acute otitis media and in respiratory syncytial virus (RSV) detections, with the greatest decreases observed among infants aged 0-2 months.

METHODOLOGY

• Researchers conducted a nationwide interrupted time-series analysis in Finland to evaluate the effect of a nationwide nirsevimab immunisation programme on acute otitis media incidence among infants younger than 12 months.
• Aggregated data from three national registers covered 181,999 infants, who contributed 2,022,261 infant-months across four RSV seasons, beginning in 2022-2023 and ending in 2025-2026.
• Finland introduced universal nirsevimab immunisation for the 2024-2025 RSV season, with doses given at maternity hospitals to newborns and to infants younger than 3 months at the start of the season.
• Researchers compared acute otitis media diagnoses and laboratory-confirmed RSV detections per 1000 infant-months during peak RSV months (December-March) between the two seasons before the implementation of the immunisation programme (2022-2023 and 2023-2024) and the two seasons after it (2024-2025 and 2025-2026), with the comparisons stratified according to age group (0-2, 3-5, and 6-11 months).

TAKEAWAY

• Among infants younger than 12 months, the incidence of acute otitis media decreased from 28.61 per 1000 infant-months at risk before the implementation of the nirsevimab programme to 15.93 per 1000 infant-months at risk after implementation, representing a 44% reduction (rate ratio [RR], 0.56; 95% CI, 0.54-0.58).
• The decline in acute otitis media incidence was largest among infants aged 0-2 months (RR, 0.31; 95% CI, 0.23-0.43), corresponding to a 69% reduction, and smallest among those aged 6-11 months (RR, 0.58; 95% CI, 0.56-0.60).
• Laboratory-confirmed RSV detections among infants younger than 12 months decreased by 83% post-implementation (RR, 0.17; 95% CI, 0.15-0.18), with the largest decrease observed among infants aged 0-2 months (RR, 0.08; 95% CI, 0.07-0.10).

INPRACTICE

"The implementation of RSV prophylaxis with nirsevimab was associated with clear reduction in AOM [acute otitis media] incidence among infants, with the largest reduction observed in the youngest age groups," the authors wrote.

"Future research should also evaluate whether maternal RSV vaccination has similar effects on AOM incidence," they concluded.

SOURCE

The study was led by Niko Leskinen, University of Eastern Finland, Kuopio, Finland. It was published online on October 9, 2026, in the European Journal of Pediatrics.

LIMITATIONS

The study lacked individual-level data on infants who received nirsevimab, preventing direct comparisons between those who received the drug and those who did not. Shifts in care-seeking, diagnostic practice, or circulation of other respiratory pathogens between seasons may have affected the rates of otitis media. Moreover, nirsevimab uptake probably affected the magnitude of the observed effect.

DISCLOSURES

The study did not receive any specific funding. The authors reported having no competing interests.

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