Colds in children do not prevent coronavirus infection, research results

The theory was simple and compelling. Children are less vulnerable to the new coronavirus because they have antibodies to other common coronaviruses that cause the common cold. This idea may also explain why some people infected with the new virus have mild symptoms and others (probably without antibodies to the common cold coronavirus) are much more seriously affected. Maybe.

This concept has attracted particular attention among those who claim that this existing protection quickly brings human populations to herd immunity. The spread of the pathogen slows down until it stops when there are no more infected hosts. A study of the journal Science published in December Made a hypothesis Powerful boost.

But because of all its charm, the theory is not supported, New study published on Tuesday In the journal cell. Based on careful experiments with live viruses and hundreds of blood samples taken before and after the pandemic, a new study found that antibodies against the seasonal coronavirus had some effect on a new coronavirus called SARS-CoV-2. I refute the idea of ​​giving.

“When we entered this study, we found that individuals who had existing pre-pandemic antibodies to SARS-CoV-2 were less susceptible to infection and had a lower severity of Covid-19 disease.” Scott Hensley said. Immunologist at the University of Pennsylvania. “It’s not what we found.”

He and his colleagues concluded that most people were exposed to the seasonal coronavirus by the age of five. As a result, about 1 in 5 people have antibodies that recognize the new coronavirus.

However, these antibodies are not neutralized. The virus cannot be disarmed or the severity of post-infection symptoms cannot be reduced.

Researchers also compared antibodies to the common cold coronavirus in children and adults and found that there was no difference in the amount. In contrast, a Science study reports that about 5% of adults carry these antibodies, compared to 43% of children.

The study “reported very high levels of pre-pandemic cross-reactive neutralizing antibodies in children, which we did not find,” Dr. Hensley said. (“Cross-reactivity” refers to antibodies that can attack similar sites of multiple types of viruses.)

“Honestly, there is no explanation for how it differs from scientific research,” he added.

Perhaps the location differences-Pennsylvania in his study and Britain in previous studies-may explain some contradictions, he said.

Other experts said Dr. Hensley’s work found the two to be more convincing and more consistent with the situation in which a large number of people were infected with the new coronavirus.

For example, one person infected with a new coronavirus at a summer camp in Wisconsin Start to occur This affected 76% of the other attendees, said John Moore, a virologist at Weil Cornell Medicine in New York.

Similarly A trawler that departed for the sea From Seattle, only three sailors who had antibodies to the new coronavirus before the trip were not infected with the virus. These are not the infection rates seen when protective antibodies are widely distributed in the population, Dr. Moore said.

“The idea of ​​protecting you from SARS-CoV-2 infections by snuffing some time ago has always kept me cold, but it was a lasting urban legend throughout the pandemic,” he said. “Hopefully, this new paper will eventually cool everyone and put such ideas in the freezer.”

Experts also praised the careful and rigorous approach of new research.

Shane Crotty, a virologist at the Lahora Institute for Immunology in San Diego, said: “I’m really happy to have done such a good study.

The theory that existing antibodies can protect people from new viruses is “arguably a strong attraction because they can blush at first and explain much of the pandemic,” Dr. Crotti said. “But beautiful ideas don’t make it happen.”

Dr. Hensley and his colleagues examined a sample of 251 people who donated blood to the University of Pennsylvania before the pandemic and then developed Covid-19.

They had levels of antibodies that could recognize the new coronavirus, which was similar to that found in blood samples taken from 251 uninfected people. And levels were not associated with clinical outcomes in any patient.

Marion Pepper, an immunologist at the University of Washington in Seattle, said: “It’s hard to get this kind of sample. I was impressed.” It’s like three different studies combined into one. “

The most important part of the coronavirus is the peplomer on its surface, which docks with human cells. Spikes are also the most characteristic part of the virus, so antibodies to seasonal viruses are unlikely to recognize and disarmament, Dr. Pepper said.

“These viruses have very specific parts that are important to infection, and most of this cross-reactivity is not directed to those parts,” she said.

However, George Kassiotis, an immunologist at the Francis Crick Institute in London, who led the study published in Science, disagreed with the conclusions of the new study. It “confirms most, not inconsistent with our main findings,” he said, adding that the new study is too small to rule out the role of existing antibodies.

But even if people actually have coronavirus antibodies from childhood infections, the protection they provide isn’t strong enough to be a problem, says Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Research Center in Seattle. Said.

“If there is no measurable effect in a study of hundreds of people in both infected and uninfected groups, the effect is certainly small,” said Dr. Bloom.

Most of the vaccines developed for the new coronavirus focus on peaplomers. Some scientists argue that antibodies against other parts of the virus may also be important for protection. However, new studies suggest that other antibodies are of minimal importance in protecting people from SARS-CoV-2.

All experts said the new study did not rule out the role of immune cells called memory B cells and T cells, which are produced in response to the seasonal coronavirus. These cells may recognize and attack some of the new viruses, reducing the severity of their symptoms.

Still, cells will not be able to prevent the infection, Dr. Crotti said. When exposed to the new virus, he said, immune cells may be triggered “fast enough to become an asymptomatic infection that went unnoticed.” “But no, they didn’t stop the infection.”

Testing for T cells is cumbersome and expensive, so analysis of their contribution to immunity has not yet been completed. Meanwhile, new research has at least ruled out the important role of existing antibodies, Dr. Hensley said: “We wrote some chapters here, but we still have a lot to learn.”