Why are children getting fewer Covid-19 symptoms, and are very unlikely to infect adults? The common cold may hold the answer.2 July 2020
A child’s body may be primed to deal with that virus because it has learned how to battle the four types of coronavirus that produce colds, which can be very debilitating but are largely harmless.
This sort of child protection is not found in other conditions, such as flu, which is also a caused by a virus.
This hypothesis is being advanced by the same scientists who are testing what they hope will be a vaccine against Covid-19, with huge British government subsidies, at Oxford University.
Other explanations have also been reported exclusively by correspondent.world. These include that children may get it so mildly and for such a short time that it cannot infect adults with whom they come into contact. Or that the ‘dose’, that is the amount of drops of liquid they put out when they breathe or sneeze or cough is much smaller, and so the virus is is less likely to be inhaled by adults.
The Oxford team have also told a parliamentary committee that they think they know what happens when the body builds up immunities or protections after exposure to common colds.
Sir John Bell, a professor of medicine at Oxford University, who is leading the Oxford team, said that for a “significant number of people” there was likely to be a “background level” of protection.
Large numbers of the adult population too may have natural immunity against coronavirus even if they have never been infected, he believes.
Research shows that T-cells, a separate part of the immune system, develop in response to chains of amino acids produced by different types of coronaviruses, his team believe.
These may stop the virus in people who never show symptoms. This means when tests fail to show that people have developed antibodies against a recurrence of Covid-19, there are other mechanisms in the body that can also provide protection but are not being tested for.
Crucially, those T-cells become ineffective or die off in older people, which may be why older people are far more likely to develop a more serious illness.
Speaking to the British parliament’s House of Commons science and technology select committee, Professor Bell said: “What seems clear is you do have cross-reaction from T-cells that are activated by standard endemic coronaviruses. I think they are present in quite a significant number of people.
“So there is probably background T-cell immunity in people before they see the coronavirus, and that may be relevant that many people get a pretty asymptomatic disease.
“Those T-cells get a bit tired once you’re beyond the age of 65 and may not be as effective at removing a virus, so that may explain a number of different features of the disease.”
The vaccine being developed by Oxford University has been found not only to stimulate antibodies but also to boost T-cell response, he revealed.
However, many more people may already have developed some protection, suggesting that the virus causing Covid-19 will naturally peter out as there are fewer and fewer people capable of being infected, the research suggests. That is known as herd immunity.
Professor Sarah Gilbert, a key part of the vaccine team, said: “It’s possible that we are underestimating natural or already-acquired immunity to this virus, and we really need to keep an eye on it.
“There is certainly evidence that people who have been infected with Covid-19 have not developed antibodies but have developed a T-cell response, and that would be likely to protect them against another infection.
“I think you have to keep an open mind about whether you have a large number of people who have protective T-cells in the absence of antibodies,” Professor Gilbert said.
Researchers at Tubingen University in Germany compared blood cells from patients who had recovered from Covid-19 with those that had not had the disease. In more than 8 out of 10 cases, even those who had not been exposed to the Covid-19 illness showed an ability to respond – because, it seems, they had previously built up some immunity to the common cold.
Their research, published in Research Square and not yet peer-reviewed, showed that previous exposure to common cold viruses made it more likely that the body would react strongly and quickly, by producing T-cells, to the invasion of the Sars-CoV-2 virus.
This is not the first time that exposure to the common cold has been linked to resistance to Covid-19 and there is some speculation that this is one of the reasons why younger people, especially children,m seem to be more immune to Covid-19 than older adults.
Exposure to the common cold could provide some measure of immunity to the disease, a new study suggests.
The key to this sort of immunity can be found in the T-cells, a type of white blood cell that helps the immune system fight off viruses, which experts believe may have just as important a role to play as antibodies in fighting off the virus.
Researchers at Tubingen University in Germany compared blood cells from patients who had recovered from Covid-19 with those that had not had the disease.
Their research, published on the pre-print server Research Square and not peer reviewed, showed that 81 per cent of the 185 people they tested who had not had the disease had a T-cell response to Sars-Cov-2, the virus that causes Covid-19.
And this immune response was linked to previous exposure to common cold coronaviruses, the researchers found.