Children account for less than 2% of identified cases of COVID-19 and an even lesser percentage of deaths. In addition, when children are infected, they often have fewer and less severe symptoms. Why? One possibility is that the SARS-CoV-2 virus is less able to bind to the epithelial cells that line a child’s nose and throat.

To test this hypothesis, researchers at the Icahn School of Medicine at Mount Sinai, New York, looked retrospectively at samples of nasal epithelium that had been collected between 2015 and 2018 in people 4 to 60 years of age as part of an asthma study (Bunyavanich S, Do A, Vicencio A. Nasal gene expression of Angiotensin-Converting Enzyme 2 in children and adults. Journal of the American Medical Association. 2020 Jun 16;323(23):2427-2429). They found that expression of the gene that codes for angiotensin-converting enzyme 2 (ACE2) was significantly less in young children (less than 10 years of age) and continued to increase in those 10 to 17 and 18 to 24 years of age. Because the spike protein located on the surface of SARS-CoV-2 binds to the ACE2 receptor on epithelial cells, this was an important finding. It appears that children may be less likely to become infected with SARS-CoV-2 simply because the virus is less capable of binding to the cells that line the child’s upper respiratory tract.

The authors concluded, “This study provides novel results on ACE2 gene expression in nasal epithelium in relation with age.”

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