This is a summary, written by members of the CITF Secretariat, of:

Sumner MW, Xie J, Zemek R, Winston K, Freire G, Burstein B, Kam A, Emsley J, Gravel J, Porter R, Sabhaney V, Mater A, Salvadori M, Berthelot S, Beer D, Poonai N, Moffat A, Wright B, Freedman SB, Pediatric Emergency Research Canada (PERC) COVID Study Group. Comparison of symptoms associated with SARS-CoV-2 variants among children in Canada. JAMA Network Open. March 9, 2023; doi:

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-supported study, published in JAMA Network Open, systematically compared the clinical manifestations of different SARS-CoV-2 variants in the pediatric population presenting in emergency departments. The authors aimed to shed more light on disease severity of the four main variants of concern (VOC)—original, Alpha, Delta, and Omicron—by comparing data collected on the presence and number of presenting symptoms (primary outcome) and on the presence of core COVID-19 symptoms, chest radiography findings and treatments, and 14-day outcomes (secondary outcomes). The study was led by Dr. Stephen Freedman (University of Calgary) in collaboration with Dr. Roger Zemek (Children’s Hospital of Eastern Ontario Research Institute), who supervised the first author Madeleine Sumner (University of Western Ontario), and co-investigators within the Pediatric Emergency Research Canada (PERC) network.

The researchers conducted a prospective observational study using data collected as part of a multi-center prospective cohort study that recruited children in 14 Canadian pediatric emergency departments (ED) between Aug 4, 2020, and February 22, 2022. Eligible participants had to be less than 18 years old and had a positive SARS-CoV-2 nucleic acid testA type of viral diagnostic test for SARS-CoV-2 result on a specimen collected from the nasopharynx, nostrils, or throat (n=1,440). The primary outcome was measured from illness onset to study enrollment. In the secondary analysis of 14-day follow-up outcomes, the authors evaluated the rates of hospitalizations, intensive care unit (ICU) admissions, and revisits to Eds or any health care provider.

Key findings:

  • The Omicron and Delta variants were more strongly associated with symptoms like fever and cough compared to the original and Alpha strains.
  • Upper respiratory tract symptoms were associated with Delta infection while lower respiratory tract and general systemic symptoms (e.g., apnea, lethargy) were more likely with Omicron infection.
  • Children with Omicron infection were more likely to undergo chest radiography, receive treatment interventions (e.g., intravenous fluids and corticosteroids), and have an ED revisit than children with Delta infection.
  • Children infected with the Alpha variant reported the fewest core COVID-19 symptoms (e.g., cough, fever, loss of small and taste).
  • No differences in secondary outcomes such as hospitalizations or ICU admissions were found across variants. However, unlike overall reports of adults experiencing less severe disease with Omicron than other variants, children continued to experience severe outcomes.

Study limitations included a degree of uncertain variant classification when inferred based on the dominant circulating strain, a lack of sufficient power for the comparison of particular symptoms, selection bias, self-reported symptoms, and an inability to separate different Omicron subvariants in the analysis, despite recognized diversity in clinical profiles.