Among the mountains of false information being peddled during the current pandemic, one of the most offensive is being used to drive opening of schools in the fall: that children do not transmit SARS-CoV-2. The results of multiple studies have shown that this assertion is incorrect. I’ll review two of them here.
One study examined 59,073 contacts of 5,706 COVID-19 patients in South Korea during January 20–March 27, 2020. The 5,706 index patients were grouped by age and the numbers of cases associated with that individual were identified. COVID-19 was detected in 11.8% of household contacts, and the rates were higher for contacts of children than for adults. The highest transmission rate, 18.6%, was observed for household contacts of school-aged children (10-19 years), and the lowest, 5.3%, for household contacts of children 0–9 years. This study was conducted in the middle of school closure; transmission rates are expected to be higher when school resumes.
A second study examined the presence of SARS-CoV-2 nucleic acids in nasopharyngeal swabs at a pediatric tertiary medical center in Chicago. The cohort, which included individuals less than a year of age to 65, all tested positive for SARS-CoV-2. Viral nucleic acid was detected by RT-PCR and the cycle threshold (CT) values for each individual were calculated. The CT value is inversely related to the quantity of nucleic acid present: the higher the number, the fewer copies of nucleic acid present in the sample.
The results show that young children (less than 5 years old) have as much or more SARS-CoV-2 nucleic acids in their upper respiratory tracts compared with older children (5-17 years old) or adults (over 18). While infectious virus was not measured, these differences mean that young children could have 10 to 100 times more infectious virus in their upper respiratory tracts.
The findings of these two studies show that young children are likely to be important drivers of SARS-CoV-2 transmission. Given the behavioral habits of young children in schools and day care centers, they will serve to efficiently amplify the virus among themselves, teachers, and their parents.
Schools may be opened only if stringent precautions are taken, including wearing of face masks, physical distancing, and most importantly, frequent testing. As discussed by Dr. Michael Mina on TWiV 640, the availability of a rapid and daily $1 test would make it possible to identify infected students and keep them at home. Unfortunately, such tests will not be widely ready for school opening this fall. Write your elected officials to demand that such tests be made available as soon as possible. There is no valid reason why we cannot achieve this goal.