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New research suggests that children can clear SARS-CoV-2, the virus that causes COVID-19, even if they never develop symptoms or for a long time after symptoms have disappeared. But many questions remain about the importance of the pediatric population as a vector for this sometimes fatal disease, according to an invited comment by physicians at Children’s National Hospital accompanying this new study published online August 28, 2020 in JAMA Pediatrics. The editorial in charge, written by Roberta L. DeBiasi, MD, MS, Chief, Division of Infectious Diseases, and Meghan Delaney, DO, MPH, Chief, Division of Pathology and Laboratory Medicine, provides important information on the role that can be play children in the spread of COVID-19 as communities continue to develop public health strategies to reign in this disease.
The study that generated this comment focused on 91 pediatric patients followed in 22 hospitals in South Korea. “Unlike the American healthcare system, those who test positive for COVID-19 in South Korea remain in the hospital until their infections clear up, even if they are not symptomatic,” explains Dr. DeBiasi.
Patients here were identified for testing by contact tracing or developing symptoms. Approximately 22% never developed symptoms, 20% were initially asymptomatic but developed symptoms later, and 58% were symptomatic on their initial test. During the course of the study, the hospitals where these children were housed continued to perform them every three days on average, providing a picture of how long viral shedding continues over time.
The study findings show that the duration of symptoms varied widely, from three days to almost three weeks. There was also a significant extension in terms of how long the children continued to shed the virus and could potentially be infectious. Although the virus was detectable for an average of about two and a half weeks in the entire group, a significant part of the children, about a fifth of the asymptomatic patients and about half of the symptomatic patients, were still shedding the virus in the three week mark.
Drs. DeBiasi and Delaney write in their comment that the study makes several important points that add to the knowledge base on COVID-19 in children. One of them is the large number of asymptomatic patients, approximately one fifth of the group followed in this study. Another is that children, a group believed to primarily develop a mild, rapidly passing illness, can retain symptoms for weeks. A third and important point, they say, is the duration of viral shedding. Even asymptomatic children continued to shed the virus for a long time after initial testing, making them possible key vectors.
However, the commentators say that despite these important findings, the study raises several questions. One concerns the link between proof and transmission. A qualitative “positive” or “negative” on the test rigs may not necessarily reflect infectivity, as some positives reflect fragments of genetic material that may not make someone sick or negatives reflect low levels of virus that may still be infectious.
Test reliability can be further limited by the same testers, with sampling across different parts of the respiratory tract or even by different staff members leading to different laboratory results. It is also unknown whether asymptomatic individuals are shedding different amounts of virus than those with symptoms, a drawback of qualitative tests performed by most laboratories. Also, tests for only active viruses rather than antibodies ignore the large number of people who may have had and cured an asymptomatic or mild infection, an important factor in understanding herd immunity.
Lastly, Drs. DeBiasi and Delaney note that the study only assessed viral shedding from the respiratory tract even though multiple studies have detected the virus in other body fluids, including feces. It is unknown what role these other sources might play in the spread of this disease.
Drs. DeBiasi and Delaney note that each of these additional findings and questions could affect public health efforts that are continually being developed and refined to control COVID-19 in the US and around the world. Children’s National has added its own research to these efforts, with ongoing studies to assess how SARS-CoV-2 infections progress in children, including how antibodies develop at both the individual and population levels.
“Each of these pieces of information that we, our collaborators, and other scientists around the world are working to collect,” says Dr. DeBiasi, “is critical to developing policies that reduce the rate of viral transmission in our community.”
