A Canadian research initiative demonstrates that a free infant immunisation programme using nirsevimab has significantly lowered severe respiratory syncytial virus cases, hospital stays, and ICU use among babies in their first RSV season.
A new Canadian study suggests a free infant immunisation programme against respiratory syncytial virus, or RSV, has delivered strong protection against the illness, sharply reducing both hospital admissions and intensive care use among babies in their first RSV season. The research, published in JAMA Network Open, found that nirsevimab, a long-acting monoclonal antibody, was highly effective when offered through universal public programmes in Ontario and Quebec. According to the study, the treatment was 79% effective at preventing hospitalisation and 97% effective at preventing ICU admission.
The findings came from the University of Calgary-led SPRINT-KIDS surveillance programme, which analysed data from seven paediatric hospitals during the 2024-25 RSV season. Sarah Buchan, the study’s first author and scientific lead for communicable disease control at Public Health Ontario, said the results showed that the intervention made a major difference in severe disease. Stephen Freedman, the senior author and SPRINT-KIDS project lead, said most babies who tested positive were otherwise healthy, with only a small minority having an underlying condition.
That point matters because RSV is a major cause of serious illness in infants, and researchers have long argued that prevention should not depend on predicting which babies will become severely unwell. Health Canada authorised nirsevimab in 2023 for newborns and infants entering their first RSV season, and Ontario and Quebec began publicly funded universal programmes in autumn 2024. Research cited in the report suggests that as many as 2% of infants born in Canada are hospitalised with RSV each year.
The new results fit with earlier evidence from JAMA, which reported strong real-world protection from nirsevimab across multiple countries, including substantial reductions in hospitalisation, intensive care admission and lower respiratory tract infection. Other JAMA Network Open studies have also found the antibody to be associated with fewer RSV-related hospitalisations in large infant cohorts, while a separate JAMA Pediatrics cohort study said the benefit was strongest in the first year after immunisation. Taken together, the evidence supports broader RSV prevention for infants during the period when they are most vulnerable.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
