The modeling study, carried out by epidemiologists at the London School of Hygiene and Tropical Medicine and published in the journal Nature Medicine, used transmission models to estimate disease susceptibility and the relation of age to cases.
Researchers estimate that clinical symptoms of Covid-19 manifest in around 21% of those aged between 10 and 19. This estimate rises to around 69% in people aged 70 or over.
Looking at epidemic data from China, Japan, Italy, Singapore, Canada and South Korea, researchers said children could be less susceptible to catching Covid-19 from contact with an infected person and could experience less severe disease.
There are still many unknowns when it comes to Covid-19, but the US Centers for Disease Control and Prevention (CDC) has said that, while some children have been sick with the virus, adults make up most of the known cases to date.
Schools around the world have been shut to prevent the spread of the novel coronavirus, and according to UNESCO estimates, more than 1.5 billion students, or more than 90% of the world’s learners, have been stuck at home due to school closures in about 190 countries.
Now, as lockdowns start to ease around the world, governments and experts are trying to navigate how — and when — children can return to the classroom.
Authors of the study said more research is needed into transmission caused by asymptomatic infections, but interventions to curb transmission that are aimed at children might have only a relatively small impact — especially if transmission from asymptomatic infections is low.
“Direct evidence for decreased susceptibility to SARS-CoV-2 in children has been mixed, but if true could result in lower transmission in the population overall,” the study said.
Countries with a lower average population age could have fewer cases of Covid-19 per capita, the study said.
“If the number of infections or cases depends strongly on the role of children, countries with different age distributions could exhibit substantially different epidemic profiles and overall impact of Covid-19 epidemics,” the study added.
Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh, said researchers found that children and teenagers were less susceptible to infection and less likely to show symptoms if infected. However, the authors were not able to determine whether young people were also less infectious, he said.
“This makes it difficult to precisely assess the impact of school closures on the wider spread of Covid-19,” Woolhouse, who was not involved in the research, told the Science Media Centre.
“Using a mathematical model the authors show that even under the most pessimistic assumption that young people are fully infectious then school closures could still have substantially less impact on the epidemic than they would for influenza-like infections,” he said.