Epidemiology and severity of pediatric influenza hospitalizations before and during the COVID-19 pandemic: a surveillance study of the Canadian immunization monitoring program (IMPACT), 2012-2023.
Pediatric influenza hospitalizations increased in 2022-2023, but severity remained lower than pre-pandemic levels, indicating a partial return to previous patterns.
Where it sits
this study against the rest of the tesofensine corpusSummary and findings
This study analyzed pediatric influenza hospitalizations in Canada from 2012 to 2023, focusing on trends before and during the COVID-19 pandemic. It included 10,091 hospitalizations, with a notable increase in 2022-2023 compared to 2021-2022. Severity indicators such as ICU admissions were lower than pre-pandemic levels.
Abstract
<h4>Background</h4>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.<h4>Methods</h4>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.<h4>Findings</h4>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.<h4>Interpretation</h4>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.<h4>Funding</h4>IMPACT is managed by the Canadian Paediatric Society and conducted on behalf of the Public Health Agency of Canada.
Background
The study addresses how the COVID-19 pandemic affected the epidemiology of pediatric influenza hospitalizations in Canada. Prior to the pandemic, influenza seasonality and severity were relatively stable. Understanding changes in these patterns is crucial for public health planning and resource allocation.
Methods
This was a national prospective surveillance study conducted through the Canadian Immunization Monitoring Program, ACTive (IMPACT), involving 12 tertiary-care pediatric centers. It included children under 17 years hospitalized with laboratory-confirmed influenza from August 2012 to August 2023. The study categorized periods as pre-pandemic and pandemic, focusing on severe disease outcomes such as ICU admission and mortality.
Results
The study observed 10,091 hospitalizations, with a significant increase in 2022-2023 compared to 2021-2022. The median age of hospitalized children increased slightly over the years. ICU admissions were lower in 2021-2022 and 2022-2023 compared to pre-pandemic levels, while mortality remained stable at 0.6%. The odds of severe disease were significantly lower during the pandemic years compared to pre-pandemic.
Interpretation
The findings suggest a partial return to pre-pandemic influenza epidemiology, with hospitalizations nearly doubling in 2022-2023. Although severity indicators increased from 2021-2022, they remained below pre-pandemic levels, indicating a potential shift in disease dynamics. The study highlights the need for ongoing surveillance to understand the long-term impacts of the pandemic on influenza patterns.
Key findings
- 10,091 total hospitalizations from 2012-2023.
- 7938 hospitalizations pre-pandemic, 335 in 2021-2022, 1810 in 2022-2023.
- Median age increased to 3.8 years in 2022-2023 (p < 0.001).
- ICU admissions: 11.3% in 2021-2022, 15.9% in 2022-2023, 17.3% pre-pandemic.
- Mortality stable at 0.6% across periods.
- Odds of severe disease lower in 2021-2022 (aOR 0.63) and 2022-2023 (aOR 0.85) vs pre-pandemic.
Limitations
- Observational study design
- Data from 12 pediatric centers only
- Potential unaccounted public health measures
- No control for regional variations