• Jared Bullard, Duane Funk, Kerry Dust, Lauren Garnett, Kaylie Tran, Alex Bello, James E Strong, Santina J Lee, Jillian Waruk, Adam Hedley, David Alexander, Paul Van Caeseele, Carla Loeppky, and Guillaume Poliquin.
• Cadham Provincial Laboratory (Bullard, Dust, Hedley, Alexander, Van Caeseele), Manitoba Health; Department of Pediatrics & Child Health (Bullard, Strong, Lee, Van Caeseele, Poliquin), University of Manitoba; National Microbiology Laboratory (Funk, Garnett, Tran, Bello, Strong, Poliquin), Public Health Agency of Canada; Departments of Anesthesiology and Medicine (Funk), Section of Critical Care, University of Manitoba; Department of Medical Microbiology & Infectious Diseases (Garnett, Tran, Bello, Alexander), University of Manitoba; Communicable Disease Control, Public Health (Lee), Manitoba Health; Epidemiology and Surveillance Unit (Waruk, Loeppky), Manitoba Health; Department of Community Health Science (Loeppky), University of Manitoba. Winnipeg, Man. jared.bullard@gov.mb.ca.
• CMAJ. 2021 Apr 26; 193 (17): E601-E606.

BackgroundThe role of children in the transmission and community spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is unclear. We aimed to quantify the infectivity of SARS-CoV-2 in nasopharyngeal samples from children compared with adults.MethodsWe obtained nasopharyngeal swabs from adult and pediatric cases of coronavirus disease 2019 (COVID-19) and from their contacts who tested positive for SARS-CoV-2 in Manitoba between March and December 2020. We compared viral growth in cell culture, cycle threshold values from the reverse transcription polymerase chain reaction (RT-PCR) of the SARS-CoV-2 envelope (E) gene and the 50% tissue culture infective dose (TCID50/mL) between adults and children.ResultsAmong 305 samples positive for SARS-CoV-2 by RT-PCR, 97 samples were from children aged 10 years or younger, 78 were from children aged 11-17 years and 130 were from adults (≥ 18 yr). Viral growth in culture was present in 31% of samples, including 18 (19%) samples from children 10 years or younger, 18 (23%) from children aged 11-17 years and 57 (44%) from adults (children v. adults, odds ratio 0.45, 95% confidence interval [CI] 0.28-0.72). The cycle threshold was 25.1 (95% CI 17.7-31.3) in children 10 years or younger, 22.2 (95% CI 18.3-29.0) in children aged 11-17 years and 18.7 (95% CI 17.9-30.4) in adults (p < 0.001). The median TCID50/mL was significantly lower in children aged 11-17 years (316, interquartile range [IQR] 178-2125) than adults (5620, IQR 1171 to 17 800, p < 0.001). Cycle threshold was an accurate predictor of positive culture in both children and adults (area under the receiver-operator curve, 0.87, 95% CI 0.81-0.93 v. 0.89, 95% CI 0.83-0.96, p = 0.6).InterpretationCompared with adults, children with nasopharyngeal swabs that tested positive for SARS-CoV-2 were less likely to grow virus in culture, and had higher cycle thresholds and lower viral concentrations, suggesting that children are not the main drivers of SARS-CoV-2 transmission.© 2021 CMA Joule Inc. or its licensors.

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