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Children may be protected from coronavirus because they catch so many colds, scientists have suggested.
Figures from the Office for National Statistics (ONS) suggest children are just as likely to pick up the virus, but few ever develop serious disease, or even show symptoms.
Now scientists have suggested that children may be resistant because their immune systems are already well primed by the common cold.
The common cold is caused by four different types of coronavirus which circulate in the community and are largely harmless. But while adults pick up a cold around two to four times a year, school age children catch an average of 12 colds annually, studies have shown.
Professor Sir John Bell, Regius Professor of Medicine, University of Oxford told the House of Lords Science and Technology Select Committee, that it may allow youngsters to build up some ongoing resistance that adults do not have.
“How you respond may be due to the state of your existing immunity to coronaviruses generally,” he told peers.
“There is an interesting speculation at the moment, that suggests that many people in young or middle aged groups may have T-cells that can already see coronavirus. It may well be able to provide some protection against this pathogen when it arrives.
“A lot of kids get seasonal coronaviruses and it’s pretty common in our population and many will have quite a strong immunity to coronaviruses generally.
“That is unproven, but there is evidence now for cross-reactivity at T-cell level at least, and that well might help dampen the effects of the virus when we get it.”
Studies have shown that by the age of four, some 70 percent of children already have antibodies against seasonal coronavirus, which could offer important protection.
Professor Adrian Hayday, Chair, Department of Immunobiology, King's College London said the immune systems of young people may simply be better at reacting to new viruses.
“All adults past a certain age - 30 to 35 - eventually have no thymus so their T-cells work by looking at whether they have seen something before, whereas children are very good at seeing things that are completely unknown.
The scientists also said that older people may suffer from immune cell ‘senescence’ where their immune cells start to shut down but are not cleared away and replaced with a working version.
senescence[sɪˈnesns]: n. 衰老
But Prof Bell said for most people coronavirus was not a serious illness.
“The people who get severe disease and die, the vast majority are elderly people and when young people get this disease they tend not to suffer very much.
“That might be the state of people’s immune system at different ages. 70 percent of the people who get this are completely asymptomatic, so at one end of the spectrum this is not a bad viral disease, at the other end it’s terrible.
“The vast majority of people who get this disease don’t even know they’ve had it.”