Under 20s Around Half as Susceptible to COVID-19, Study Finds

By Kate Kelland

June 17, 2020

LONDON (Reuters) - People under 20 are around half as susceptible to infection with SARS-CoV-2 as people aged 20 or above, according to a modeling study published on Tuesday, and clinical symptoms of COVID-19 appear in only about a fifth of infections in children and teens.

By contrast, the model suggests, COVID-19 symptoms appear in 69% of infections in people aged 70 or older.

The estimates are drawn from data collected in 32 locations in China, Italy, Japan, Singapore, Canada and South Korea.

The findings suggest that school closures - introduced in many countries as part of lockdowns aimed at controlling the coronavirus pandemic - are likely to have a limited impact on transmission of the disease, the researchers said.

Published in the journal Nature Medicine, the study compared the effect school closures on simulated outbreaks of flu - which is known to spread swiftly in children - and of COVID-19, the disease caused by the new coronavirus.

"For COVID-19, there was much less of an effect of school closures," said Rosalind Eggo, an infectious disease modeller at The London School of Hygiene and Tropical Medicine who co-led the study.

She added, however, that the findings come from simulated outbreaks and need to be reinforced with real-world research.

Using demographic data from the six countries, as well as from six studies on estimated COVID-19 infection rates and symptom severity across different age groups, the model showed that people under 20 are about half as susceptible to the virus as people over 20, and that among 10 to 19 year-olds, only 21% of those infected had clinical symptoms.

The researchers also simulated COVID-19 epidemics in 146 capital cities around the world and found that the total expected number of clinical cases varied with median age.

"The age structure of a population can have a significant impact," said Nicholas Davies, who co-led the work. "Countries with more young people may experience a lower burden of COVID-19."

A separate study published in the same journal by U.S. researchers used age-specific coronavirus mortality patterns together with demographic data to map projections of the cumulative case burden of COVID-19 and the subsequent burden on healthcare resources. "We observed a general pattern that per capita disease burden and relative healthcare system demand may be highest away from major population centers," concluded Ian Miller of Princeton University and colleagues.

SOURCE: https://go.nature.com/3fmw9wS and https://go.nature.com/3hAYKAg Nature Medicine, online June 16, 2020.