Population-based study demonstrates marked reductions in RSV hospitalizations in young infants, highlighting the real-world impact of universal nirsevimab immunization.
Key Points
To evaluate the population-level impact of a universal infant nirsevimab immunization program on RSV-related emergency department visits and hospitalizations among infants aged 0 to 5 months.
Evaluated health outcomes across all Québec children younger than 18 years during the 2024–2025 season compared with historical seasons using active surveillance and administrative health data.
Calculated incidence rates of RSV-confirmed hospitalizations, RSV-associated hospitalizations, RSV-associated emergency department visits, and acute bronchiolitis visits in eligible infants (0–5 months) and non-eligible age groups.
Employed difference-in-differences and constant proportion of admissions counterfactual models to adjust for background secular trends observed in non-targeted cohorts.
In infants aged 0–5 months, RSV-confirmed hospitalizations decreased by 59% (95% CI: 49–70%) and RSV-associated hospitalizations decreased by 66% (95% CI: 58–71%).
RSV-associated emergency department visits declined by 60% (95% CI: 56–65%), and acute bronchiolitis emergency visits fell by 35% (95% CI: 28–41%).
Counterfactual models estimated that the immunization campaign prevented between 323 and 746 infant hospitalizations during the 2024–2025 season.