Scientists are understanding why some people avoid COVID-19

Ashish Jha, the White House’s COVID-19 response coordinator, said Thursday that most people in the U.S. have been infected with COVID-19 at least once — probably more than 70% of the country — based on data from the Centers for Disease Control and Prevention.

Many are infected more than once. In a preliminary study of 257,000 US veterans who contracted COVID-19 at least once, 12% were reinfected by April and about 1% were infected three or more times.

This raises the obvious question: What is preventing fewer people from getting sick?

In addition to individual behavior, disease experts are studying the effects of multiple predictors, including genetics, T-cell immunity, and inflammatory conditions such as allergies and asthma.

But even as experts learn more about why people may be better equipped to protect themselves from COVID-19, they warn that some of these defenses may not hold up to the latest version of omicron BA.5. vaccine protection.

“It really takes two to tango,” said Neville Sanjana, a bioengineer at the Genome Center in New York. “If you think about an infection and the bad things that follow, it’s really the product of two different organisms: the virus and the person.”

Genetics may reduce risk of COVID-19

In 2020, New York University researchers identified a number of genes that influence a person’s susceptibility to the coronavirus. Specifically, they found that inhibiting certain genes that code for a receptor called ACE2, which allows the virus to enter cells, reduced a person’s chance of infection.

Sanjana, who conducted the study, estimated that between 100 and 500 genes may influence susceptibility to COVID-19 in the lungs or nasal cavity.

Genetics “could make a big contribution” to protection against COVID-19, he said. “I would never say it’s the only contribution.”

In July, researchers identified a common genetic factor that may affect the severity of coronavirus infection. In a study of more than 3,000 people, two genetic variations reduced the expression of a gene called OAS1, which is part of the innate immune response to viral infections. This was associated with the risk of hospitalization for COVID-19.

Therefore, increasing gene expression should have the opposite effect—increased risk of severe disease—but it may not completely prevent infection.

“It’s natural to get infected after an overdose. There is no magic bullet for this. But once you get an infection, how you respond to that infection is what affects your genetic variants,” said Lyudmila Prokunina-Olsson, the study’s principal investigator and head of the Translational Genomics Laboratory. National Cancer Institute.

Still, Benjamin TenOver, a professor of microbiology at the NYU Grossman School of Medicine who helped lead the 2020 study, said it’s difficult for scientists to identify a specific gene responsible for preventing infection with COVID-19.

“There may still be some genetics that make people completely resistant, but they will be very difficult to find,” tenOever said. “People have been searching hard for two years now, with no results.”

Photo: A man receives a Covid-19 test outside the Salt Lake County Health Department on July 22, 2022. (Rick Baumer/AP)

T cells can remember previous coronavirus encounters

In addition to this new SARS-CoV-2 coronavirus, four other coronaviruses commonly infect humans, which usually cause mild to moderate upper respiratory illnesses like the flu.

A recent study suggests that repeated or occasional infections with this common cold coronavirus may provide some protection against SARS-CoV-2.

The researchers found that T cells, a type of white blood cell that recognizes and fights invaders, appear to recognize SARS-CoV-2 based on previous exposure to other coronaviruses. So when someone who has contracted the common cold coronavirus is later exposed to SARS-CoV-2, they may not be as sick.

However, this T-cell memory does not completely prevent COVID-19.

“While neutralizing antibodies are key to preventing infection, T cells are key to stopping infection and modulating the severity of infection,” said study author Alessandro Sette, a professor at the La Jolla Institute of Immunology.

According to Seth, some people’s T cells clear the virus so quickly that the person never tests positive for COVID-19. But researchers aren’t yet sure what exactly is going on.

“It’s possible that even though the test was negative, it was a very abortive, transient infection that went undetected,” Sette said.

At the very least, he said, T cells from previous COVID-19 infections or vaccines should offer some protection against coronavirus variants, including BA.5.

Allergies may provide some additional protection

Although asthma has been viewed as a potential risk factor for severe COVID-19 during the pandemic, recent research suggests that low-level inflammation from conditions such as allergies or asthma may have protective benefits.

“You hear these stories about some people who are sick and have full-on symptoms of COVID, and during that time they sleep next to their partner for a week without giving it to them. People think they must have some sort of genetic resistance to it. [but] A big part of that could be if the partner next to them somehow has a higher normal inflammatory response in their lungs,” tenOever said.

A May study found that nearly 1,400 US households with food allergies had a halved risk of contracting the coronavirus. In the study, asthma did not reduce people’s risk of infection, but neither did it increase it.

One theory, the researchers say, is that people with food allergies show fewer ACE2 receptors on the surface of airway cells, making it harder for the virus to enter.

“Because there are fewer recipients, you’re going to have a much lower infection rate or be less likely to get an infection,” said Tina Hartert, M.D., professor of medicine and pediatrics at Vanderbilt University School of Medicine. the research.

The study took place from May 2020 to February 2021, before the omicron variant became available. But Hartert said BA.5 does not eliminate cross-protection against allergies.

“If something like allergic inflammation is protective, I think that’s true for all options,” Hartert said. “The degree to which it can be protected can certainly vary.”

Infection with BA.5 is more difficult to avoid

For many people, the first explanation that comes to mind when thinking about avoiding COVID-19 is a person’s level of personal precaution. NYU’s TenOever believes that individual behavior, rather than genetics or T cells, is the key factor. He and his family in New York are among the few who have never contracted COVID-19, citing precautions like staying home and wearing masks.

“I don’t think there’s anything special about our genetics that makes us resilient,” he said.

It is now common knowledge that the majority of the spread of the COVID-19 virus was easily preventable down to the micron, when a small percentage of infected people were responsible. A 2020 study, for example, found that 10% to 20% of infected people account for 80% of infections.

But omicron and its subvariants have made any social interaction unsafe for all involved.

“It’s probably more of a level playing field with the omicron options than the previous options,” tenOever said.

BA.5, in particular, increased the likelihood of getting sick in people who had previously avoided COVID-19. President Joe Biden is a prime example: He tested positive for the first time this week.

But still, Jha said at a briefing Thursday, “I don’t believe every American has been infected.”

This article originally appeared NBC News.

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