Study provides clues about childhood immunity and COVID-19

A child pumps hand sanitizer in a partially-filled classroom of students practicing social distancing during the pandemic.

Children may spread SARS-CoV-2, the pathogen that causes COVID-19, at a higher rate than previous research suggested, according to a study published in the Journal of Pediatrics and funded by the National Heart, Lung, and Blood Institute.

Harvard researchers at Massachusetts General Hospital (MGH) invited patients, ages 0-22, receiving urgent care for COVID-19 symptoms to participate in a clinical trial. The goal of the study was to assess how children expressed physical symptoms, carried viral loads of SARS-CoV-2, and recovered. Patients contributed nose, throat, or blood samples to the COVID-19 pediatric biorepository.

The researchers found children of all ages, from preschool to college, carried higher loads of the virus than adults, especially within the first two days of expressing symptoms. Symptoms observed in the study included coughing, congestion, headaches, and runny noses, similar to respiratory tract infections, but with higher rates of sore throats and loss of smell.

The researchers suspect COVID-19 transmission in children is similar to other viruses, like the flu, but they did not study how children transmit COVID-19. The study supports school reopening strategies to reduce COVID-19 transmission and mitigate post-infection pediatric complications, including multisystem inflammatory syndrome in children (MIS-C).

Out of 192 children in the study, 49 tested positive for COVID-19. About half of pediatric patients in the study with COVID-19 had a fever. However, one in three children with COVID-19 remained symptom-free. They sought testing after being exposed to someone with the virus.

Eighteen children tested positive for MIS-C, an uncommon but severe immune reaction that can happen weeks after infection. MIS-C symptoms resemble Kawasaki disease, a rare childhood condition, and may include fever, vomiting, and a rash. The remaining children tested negative for COVID-19, but had similar flu- and cold-like symptoms.

Based on the data, which proved COVID-19 infections were hard to predict in children based on physical symptoms, researchers recommend schools use physical distancing measures, such as social distancing, masking, and virtual learning, to reduce risk for transmission. This advice varies from monitoring physical symptoms, such as daily temperature checks to identify COVID-19 infections in students. Routine screenings, including testing, can complement these efforts. However, children with MIS-C carry smaller loads of the virus.