A new immunisation offered free of charge to all infants through universal programmes in two Canadian provinces has demonstrated strong protection against respiratory syncytial virus (RSV), substantially reducing both hospitalisations and admissions to ICUs. The findings, published in JAMA Network Open, assessed the real-world effectiveness of nirsevimab, a long-acting monoclonal antibody that provides infants with ready-made antibodies to protect against severe RSV disease. The study was conducted by the University of Calgary-led Surveillance Program for the Rapid identification and tracking of Infectious Diseases in kids (SPRINT-KIDS).
RSV is a major cause of hospitalisation among infants, and the researchers sought to determine how effectively nirsevimab prevented severe disease during an infant’s first RSV season. Dr Sarah Buchan, first author of the study and scientific lead for Communicable Disease Control at Public Health Ontario, reported that the results showed substantial protection. Nirsevimab was 79% effective against RSV-related hospitalisation and 97% effective against ICU admission.
The researchers analysed data from the 2024–2025 RSV season collected at seven paediatric hospitals in Ontario and Quebec.
An important finding was that the majority of infants who developed RSV infection had no underlying health problems. According to Dr Stephen Freedman, senior author and SPRINT-KIDS project lead, only 3% of infants who tested positive for RSV had a comorbidity. This finding supports a universal approach to RSV prevention rather than limiting protection to infants considered at greater risk. Providing nirsevimab to all infants offers protection during a period of particular vulnerability without requiring clinicians to predict which children are most likely to develop severe disease.
Previous research suggests that up to 2% of infants born in Canada are hospitalised with RSV each year. Health Canada authorised nirsevimab in 2023 for the prevention of RSV lower respiratory tract disease in newborns and infants entering or experiencing their first RSV season. In autumn 2024, Ontario and Quebec introduced publicly funded universal programmes that made nirsevimab available to all infants.
The SPRINT-KIDS Network carries out surveillance activities with funding from the Public Health Agency of Canada. It comprises 14 paediatric hospitals across eight provinces and conducts real-time surveillance of respiratory viruses and vaccine effectiveness in children. This work helps identify changes in patterns of viral activity and provides timely evidence to inform public health policy and clinical practice. SPRINT-KIDS surveillance data are publicly available through its online dashboard and are also incorporated into the Government of Canada’s respiratory virus surveillance reporting.
Source: University of Calgary
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