Changes in Pediatric RSV Hospitalizations after the COVID-19 Pandemic, 2022-2023, Canada: An Active Surveillance Study

BackgroundThe COVID-19 pandemic impacted RSV epidemiology. We describe Canadian pediatric tertiary care RSV hospitalizations in 2022-2023 and assess pandemic-related changes. MethodsActive surveillance of hospitalized children aged 0-16 years was conducted at 13 Immunization Monitoring Program, Active (IMPACT) centres. RSV hospitalizations in 2022-2023 were compared to those in the pre-pandemic period (2017-2018 through 2019-2020). Province-specific and age-stratified proportions of all-cause hospitalizations with RSV detection and age-stratified proportions of RSV-associated intensive care unit (ICU) admission were calculated. Changes in seasonality were assessed using Seasonal Autoregressive Integrated Moving Average (SARIMA) modelling. ResultsIn 2022-2023, there were 5362 RSV-associated hospitalizations including 1260 (23.5%) ICU admissions, both more than double pre-pandemic yearly averages. Overall, median (IQR) age increased from 6 months (1-20) to 9 months (2-27; P<0.001). The proportion of RSV hospitalizations among all-cause hospitalizations increased by 3.5 percentage points (95% CI 3.3-3.7 percentage points), to 6.8% (95% CI 6.6%-7.0%). While 41.5% of RSV hospitalizations were among children <6 months old, they accounted for 62% of ICU admissions. Overall, ICU proportion remained constant; however, odds of ICU admission among infants <6 months old increased (adjusted OR 1.35, 95% CI 1.2-1.52) compared to the pre-pandemic period. National weekly incidence in 2022-2023 peaked earlier, higher and persisted longer than expected by SARIMA. InterpretationsIn 2022-2023, the number of RSV hospitalizations and ICU admissions increased dramatically in Canadian pediatric hospitals. Despite an older age distribution, the greatest burden remained in children <6 months old. RSV immunization strategies for young infants will likely have substantial potential public health impact.