As the start of the school year approaches, researchers sough to analyze the transmission potential of SARS-CoV-2 among children to better understand risks associated with re-opening schools. Results of this analysis found that children aged <5 years were found to have significantly greater levels of viral nucleic acid (RNA) in their nasopharyngeal swab results compared with older children and adults, suggesting that young children have an increased potential to spread COVID-19 in daycare and school settings, according to a research letter published in JAMA Pediatrics.

The researchers performed SARS-CoV-2 RT-PCR testing at several inpatient, outpatient, emergency department, and drive-through testing sites between March 23 and April 27, 2020. Researchers recorded PCR amplification cycle threshold (CT) values; lower values indicated higher amounts of viral nucleic acid.

The study included all individuals aged <1 month to 65 years who tested positive for COVID-19. Patients who required supplemental oxygen support (n=7), asymptomatic patients (n=7), patients with unknown duration of symptoms (n=29), and patients whose symptoms started >1 week prior to testing (n=19) were excluded from the final cohort of 145 patients with mild to moderate illness who were tested within 1 week of symptom onset. Patients were grouped into 3 categories by age: children aged <5 years (n=46), children aged 5 to 17 years (n=51), and adults aged 18 to 65 years (n=48).

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Young children were found to have equivalent or more viral nucleic acid in their upper respiratory tract (median CT values 6.5) compared with older children (median CT values 11.1) and adults (median CT values 11.0). These differences in CT values between young children and older patients “approximate for a 10-fold to 100-fold greater amount of SARS-CoV-2 in the upper respiratory tracts of young children,” noted the researchers.

When the 29 patients with unknown symptom duration were included for a sensitivity analysis, researchers observed a similar difference between patient age groups. The authors identified a very weak correlation between symptom duration and CT in the overall cohort (P = 0.22) and in each subgroup (young children P= 0.20; older children P= 0.19; adults P= 0.10).

“Behavioral habits of young children and close quarters in school and daycare settings raise concern for SARS-CoV-2 amplification in this population as public health restrictions are eased,” researchers said. “In addition to public health implications, this population will be important for targeting immunization efforts as SARS-CoV-2 vaccines become available.”

Disclosures: Dr Muller has received grants from Ansun BioPharma, Astellas Pharma, AstraZeneca, Abbott Laboratories, Janssen Pharmaceuticals, Karius, Merck, Melinta Therapeutics, Roche, Tetraphase Pharmaceuticals, and Seqirus. Dr Patel has received grants from Aqua Pharmaceuticals. Dr Kociolek has received grants from Merck.


Heald-Sargent T, Muller W, Zheng X, Rippe J, Patel A, Kociolek L. 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) [published online July 30, 2020].  JAMA Pediatr. doi:10.1001/jamapediatrics.2020.3651.