Older children and the Coronavirus: A new wrinkle in the debate

A study by researchers in South Korea last month suggested that children between the ages of 10 and 19 spread the coronavirus more often than adults – a widely reported finding that has influenced the debate over the risks of schooling.

But additional data from the research team now casts doubt on that conclusion; it is not clear who infected with whom. The incident underscores the need to consider the preponderance of evidence, rather than any single study, when making decisions about children’s health or education, scientists said.

In fact, some of the household members who appeared in the first report to be infected by older children were exposed to the virus at the same time as the children. All of them may have been infected by contacts they shared.

The revelation does not ignore the general message of that study, experts said: Children under the age of 10 do not spread the virus as much as adults do, and the ability to transmit seems to increase with age.

“The most important point of the paper is that it makes it clear where we need to interpret individual studies, in particular about transmitting a virus, where we know the dynamics are complex,” said Dr Alasdair Munro , Clinical Research Fellow in Infection for Pediatric Diseases at University Hospital Southampton in the United Kingdom.

The previous study was not intended to demonstrate the transfer of children to adults, only to describe contact tracing efforts in South Korea, Drs. Young June Choe, assistant professor of social and preventive medicine at Hallym University College of Medicine and an author of both studies.

Most studies of transmission of children have been observational and have not followed infected children because they spread the virus. The few studies studied are not directly comparable – their methods, prevention policies and transmission levels in communities all differ widely.

Many studies have grouped children of widely varying ages. However, a 10-year-old is likely to be very different from a 20-year-old in terms of infection risk and transmission, as well as in type and level of social activity, Drs. Munro.

The first study from South Korea attempted to document the immediate transfer of children, but it grouped them into 10-year range. Finding the contacts of 29 children aged 9 or younger found that the children were about half as likely as adults to spread the virus to others, consistent with other research.

Mar Dr. Choe and his colleagues reported an early finding in the group of 124 children aged 10 to 19: They appeared to be significantly more likely than adults to spread the coronavirus. Experts at the time told The Times that the finding was likely a fluke.

The group of older children was not the same in both studies, but many appeared in both reports, said Drs. Choe. In the latest study, investigators found only one undeniable case of transmission among older children, from a 16-year-old girl, who had returned from Britain, to her 14-year-old sister.

The remaining 40 infected contacts of the older children could all be explained by a shared exposure.

The children with confirmed infections were isolated in hospitals as centers for community treatment, and caregivers who had contact with them were required to wear masks, gloves, a full body suit and goggles. The low rate of transmission of older children observed here may not represent what is happening in the real world.

The new report suggests that older children are at least less likely to transmit than adults, said Natalie Dean, a biostatistician at the University of Florida, as originally claimed.

“There is no biological explanation for that,” she said. “It made no sense to me.” About everything added Dr. Dean, “We don’t see much real child transfer.”

But that may be because most studies have been too small to adequately distinguish between age groups, and because children are kept at home, away from possible exposures.

Even if the risk of transmission of children is lower, they normally have contact with a large number of other people – more than the average adult. When schools reopen, these increased exposures create more opportunities to transmit the virus, which may counteract their lower propensity to transmit the virus.

Dr. Dean and other experts have warned against interpreting the scientific evidence so far that they say children under the age of 10 simply cannot spread the coronavirus.

But “it’s not true to say they do not transmit,” said Bill Hanage, an epidemiologist at the Harvard TH Chan School of Public Health. “You hear people say this, and it’s wrong.”

All available evidence to date makes it clear that older children, especially those closest to adulthood, can spread the virus as much as adults, he added.

“It is undisputed that the highest risk of becoming infected and being detected is infected in older age groups,” said Drs. Hanage. “I think you have to be really careful before you decide to open high schools.”

Talks about reopening schools are complicated because so much depends on the level of transfer of the community and on socio-economic factors, he and other experts said.

Schools can increase the spread of the flu virus disproportionately, compared to restaurants, bars or places of worship. Children are allowed to ride these outbreaks, so closing schools during flu outbreaks makes sense, said Drs. Hanage.

But with the coronavirus, Drs. Hanage, “Closing schools is not expected to cause them more fear of money than closing other parts of society.” Instead of opening bars and restaurants along with schools, he said, schools should be given priority, while bars and restaurants should be closed to reduce communication transmission and allow reopening of schools.