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Pediatric COVID-19 severity by SARS-CoV-2 lineage and vaccine status in Canada: an IMPACT study
Daniel S Farrar1, Julie A Bettinger2,3, Aaron J Campigotto4
1Centre for Global Child Health, The Hospital for Sick Children, Toronto, ON, Canada.
Insights
COVID-19 hospitalizations in children increased with Omicron lineages, but vaccination reduced severe disease risk in older children. Vaccines also lowered overall hospitalization rates for children aged 5-16 years.
Area of Science:
- Pediatric Infectious Diseases
- Epidemiology
- Vaccinology
Background:
- Pediatric COVID-19 severity is influenced by evolving SARS-CoV-2 variants and vaccine availability.
- Understanding these factors is crucial for public health strategies.
- Canadian surveillance data provides insights into these trends.
Purpose of the Study:
- To estimate the risk of severe COVID-19 in hospitalized Canadian children based on SARS-CoV-2 lineage.
- To assess the impact of COVID-19 vaccination status on disease severity.
- To analyze trends across different Omicron sub-lineages.
Main Methods:
- Utilized data from the Canadian Paediatric Surveillance Program and Canadian Immunization Monitoring Program, ACTive.
- Included children under 17 hospitalized for COVID-19 from April 2020 to December 2022.
- Defined severe disease and identified SARS-CoV-2 lineages through genetic sequencing or dominant lineage analysis.
Main Results:
- Omicron lineages accounted for 81.4% of hospitalizations; more children were hospitalized with Omicron than all prior lineages combined.
- Severe COVID-19 was common during Omicron (27.2%) and Delta (23.2%) periods.
- Vaccination reduced severe disease risk in 12-16 year olds (aRR 0.49) and hospitalization in 5-16 year olds.
Conclusions:
- Omicron lineages led to a higher burden of pediatric COVID-19 hospitalizations compared to previous strains.
- COVID-19 vaccination demonstrated a protective effect, reducing severe disease and hospitalizations in specific pediatric age groups.
Background:
Interpretations of pediatric COVID-19 severity are complicated by novel lineages and COVID-19 vaccine introduction. We estimated the risk of severe COVID-19 by SARS-CoV-2 lineage and vaccination status among hospitalized Canadian children.
Methods:
Data were collected through the Canadian Paediatric Surveillance Program (April 2020-May 2021) and Canadian Immunization Monitoring Program, ACTive (June 2021-December 2022). Patients <17 years hospitalized for COVID-19 (excluding incidental SARS-CoV-2) at 13 pediatric hospitals were included. Lineages were defined via genetic sequencing or dominant lineage upon hospitalization. Severe disease included intensive care, ventilatory/hemodynamic requirements, systemic complications, and/or death.
Results:
We analyzed 3218 COVID-19 hospitalizations, including 81.4% admitted during Omicron predominance. Median age was highest among Delta cases (2.9 years, interquartile range [IQR] 0.2-10.9) and lowest among Omicron BQ.1 cases (0.6 years, IQR 0.2-1.8). Severe COVID-19 remained common in Omicron vs. ancestral cases (27.2% vs. 23.2%). The proportion of hospitalized cases aged 5-16 years declined following the introduction of age-specific COVID-19 vaccines. Vaccination reduced the risk of in-hospital severe disease for ages 12-16 years (two vs. zero doses; adjusted risk ratio 0.49, 95% confidence interval 0.32-0.77).
Conclusion:
More children were hospitalized with Omicron lineages than all prior lineages. COVID-19 vaccination was associated with a lower burden of severe disease among ages 5-16 years.
Impact Statement:
This study estimates the effect of SARS-CoV-2 lineage, Omicron sub-lineage, and vaccination on COVID-19 disease severity, using data from two Canadian national surveillance programs. Few national studies describe the clinical presentation and severity of Omicron sub-lineages among hospitalized children. In Canada, Omicron lineages were associated with substantially more pediatric COVID-19 hospitalizations than all prior lineages combined, though risk of severe COVID-19 was highest during the Delta period. COVID-19 vaccines were associated with reductions in hospitalization (ages 5-16 years) and severe disease (ages 12-16 years) across Omicron sub-lineages.
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