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Comment & Response
February 1, 2021

Viral Loads of SARS-CoV-2 in Young Children

Author Affiliations
  • 1Institute for Genome Sciences, Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore
JAMA Pediatr. 2021;175(5):529. doi:10.1001/jamapediatrics.2020.5545

To the Editor I have concerns about the methodology, which influences the results and conclusions, reported in a recent article on coronavirus disease 2019 samples that has garnered attention because of its implications for important public health decisions. In “Age-Related Differences in Nasopharyngeal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Levels in Patients With Mild to Moderate Coronavirus Disease 2019 (COVID-19),” Heald-Sargent et al1 compare cycle threshold (Ct) values for different cohorts of patients with coronavirus disease 2019 grouped by age. Most of the data appear to be for Ct values that were less than 11. The median Ct was 6.5 for children younger than 5 years, meaning half of the samples had a Ct value of 6.5 or less. Looking at the range in the plots, it appears some data points may have had a Ct near 3. Yet, Ct values typically are not quantitative in these ranges, and the authors did not include or refer to a standard curve to demonstrate that the values were quantitative in this range. Other related studies2,3 use Ct values in a range that is typically found to be more quantitative (Ct >14), which can be achieved by diluting the samples prior to testing. Given this problem, the conclusion that the virus is higher in children may not be supported by these data. The article seemingly still demonstrates that the virus can be found at high levels in these samples from these age groups, at least for many of these samples.

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