Background The COVID-19 pandemic disrupted respiratory virus circulation, including influenza. We described trends in seasonality, demographics, and severity of pediatric influenza hospitalizations in Canada before and during the pandemic. Methods We conducted national prospective surveillance through the Canadian Immunization Monitoring Program, ACTive (IMPACT), across 12 tertiary-care pediatric centers. Children <17 years hospitalized with laboratory-confirmed influenza between August 2012–August 2023 were included. Periods were categorized as pre-pandemic (2012–March 2020), and pandemic (2021–2022, 2022–2023). Severe disease was defined as intensive care unit (ICU) admission, mechanical ventilation, extracorporeal membrane oxygenation, and/or death. Adjusted odds ratios (aOR) were estimated using multivariable logistic regression. Findings Among 10,091 hospitalizations, 7938 occurred pre-pandemic (annual average=955), 335 in 2021–2022, and 1810 in 2022–2023. The median age was 3.0 (IQR 1.2–6.4) in pre-pandemic, 3.3 (IQR 1.4–7.3) in 2021–2022, and 3.8 years (IQR 1.7–7.2, p < 0.001) in 2022–2023. ICU admissions declined in 2021–2022 (11.3%) and rose in 2022–2023 (15.9%), though remaining below pre-pandemic levels (17.3%). Mortality was stable across periods (0.6%). The odds of severe disease were lower in 2021–2022 (aOR 0.63, 95% CI 0.44–0.89) and 2022–2023 (aOR 0.85, 95% CI 0.74–0.98) compared to pre-pandemic. Interpretation Pediatric influenza hospitalizations nearly doubled in 2022–2023, with a modest shift in age distribution toward older children. Although severity indicators rose compared to 2021–2022, they remained slightly reduced compared to pre-pandemic seasons, suggesting suggest a partial return toward pre-pandemic epidemiologic patterns. Funding IMPACT is managed by the Canadian Paediatric Society and conducted on behalf of the Public Health Agency of Canada.
Chiara et al. (2026) studied this question.