Under 20s around half as susceptible to Covid-19, study finds

The research found that coronavirus symptoms appear in 69 per cent of infections in people aged 70 or older

FILE - In this April 17, 2020, file photo, using her phone as a mirror, Evie Altman, center, checks out her haircut that her son Marxe Orbach, 19, left, did as daughter Satch Orbach, 17, right, watches from the garage of their Bethesda, Md., home. Altman let her son cut her hair and then she cut his making this adventure a family affair. Americans are more unhappy today than they’ve been in nearly 50 years. That's according to the COVID Response Tracking Study, conducted in late May by NORC at the University of Chicago. (AP Photo/Susan Walsh, File)
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People under 20 are around half as susceptible to Covid-19 as people aged 20 or above, according to research published on Tuesday, and clinical symptoms of the pandemic disease appear in only about a fifth of infections in children and teens.

The research, a modelling study using data from 32 locations China, Italy, Japan, Singapore, Canada and South Korea, found that by contrast, Covid-19 symptoms appear in 69 per cent of infections in people aged 70 or older.

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 Covid-19 as people over 20, and that among 10 to 19 year-olds, only 21 per cent 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."