Children May Be Less Likely Than Adults to Have Asymptomatic SARS-CoV-2

As schools reopen around the world, infectious diseases experts have focused on better understanding the risk of children being asymptomatic spreaders of SARS-CoV-2. A new research letter by investigators in Italy suggests that risk may not be as high as some have feared.

The retrospective analysis, published in JAMA Pediatrics, looked at emergency department patients hospitalized during the coronavirus disease 2019 (COVID-19) pandemic lockdown from March 1 to April 30 at one hospital in Milan.

Out of 83 children admitted without any signs of symptoms of SARS-CoV-2 infection, 1 tested positive for the virus (1.2%). That compares with 12 of 131 adults (9.2%) who tested positive during the same time.

“The data do not support the hypothesis that children may be asymptomatic carriers more than adults,” Carlo Agostoni, MD, Pediatric Intermediate Care Unit, Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico, Milan, Italy, told Contagion.

The study included patients admitted for non-infectious conditions, including surgical intervention, neurologic disease, trauma, cardiac disease, psychiatric disorder, intoxication and other conditions. Median age of children in the study was 5, and median age of adults was 77. They received nasopharyngeal swab tests for SARS-CoV-2 immediately and, if the results were negative, they received a second test within 12 to 48 hours.

“When we started to check the data of the lockdown period in our two ER Units (Pediatric and Adult, respectively) we had no clear hypothesis,” Agostoni said. “As reported in our paper, while children were suggested to possibly be facilitators of SARS-CoV-2 transmission and amplification since most of them are asymptomatic (Lancet 2020;20:633), on the other hand a report from China published in the NEJM (2020:382:1663) suggested that asymptomatic children were about 15% of individuals positive for SARS-CoV-2.”

None of the study participants developed symptoms of COVID-19 in the 48 hours after admission.

“We stress once more that these data do not support the hypothesis that children may be asymptomatic carriers more than adults,” Agostoni said. “Nevertheless, the survey should be considered within its limited setting, that is, a retrospective analysis of cases accessing the ER and requiring hospitalization within a unique hospital in the lockdown period.”

He said the study, in combination with recommendations of social distancing and wearing masks, could contribute to a less pessimistic view as schools reopen.

“We strongly recommend to be on guard in any case,” Agostoni said. “Larger sets of data from comparable settings and environments are expected to better compose and understand this puzzling situation. Unfortunately, the wide heterogeneity of methods of directly detecting the virus and/or antibody identification could represent a further bias in the correct interpretation of data.”

Other research is ongoing to understand the risks of COVID-19 spreading among children. A team from the University of California San Francisco developed a Pediatric COVID-19 Risk Assessment Tool, estimating that 1% of all children in some areas of US are asymptomatic carriers of SARS-CoV-2.

Even small prevalence rates of asymptomatic infection from 1-3% could lead to outbreaks in classrooms, Dylan K. Chan, MD, of the University of California San Francisco (UCSF) Division of Pediatric Otolaryngology, Department of Otolaryngology—Head and Neck Surgery, told Contagion in an interview published in early September. He pointed out that current understandings of the virus include that older children and adolescents are shedding more virus than younger children.

Testing guidance from the Centers for Disease Control and Prevention was clarified Sept. 18, to include recommendations that asymptomatic people who have been in close contact (≤6 feet) for at least 15 minutes with a person who has a documented SARS-CoV-2 infection receive a test.