ding an infection and modulating the severity of the infection,” said Alessandro Sette, study author and professor at the Institute. La Jolla of Immunology.
Sette said it’s possible that some people’s T cells clear the virus so quickly that the person never tests positive for Covid. But researchers don’t yet know if that’s what’s happening.
“It’s possible that despite the negative test result, it was a very abortive transient infection that went undetected,” Sette said.
At the very least, he said, T cells from previous Covid infections or vaccines should continue to offer some protection against coronavirus variants, including BA.5.
Allergies can lead to a little extra protection
Although asthma was considered a potential risk factor for severe Covid at the start of the pandemic, more recent research suggests that low-grade inflammation due to conditions such as allergies or asthma may have a protective effect.
“You will hear these stories of people getting sick and showing full symptoms of Covid, and having slept next to their partner for an entire week during this time without giving it to them. People think they must have some genetic resistance to it, [but] a lot of that could be if the partner next to them somehow has a higher than normal inflammatory response in their lungs,” tenOever said.
A can study found that having a food allergy halved the risk of coronavirus infection in nearly 1,400 US households. Asthma did not reduce people’s risk of infection in the study, but it did not increase it either.
One theory, according to the researchers, is that people with food allergies express fewer ACE2 receptors on the surface of their airway cells, making it harder for the virus to enter.
“Because there are fewer receptors, you’ll either have a much lower grade infection or just be less likely to get infected,” said Tina Hartert, a professor of medicine and pediatrics at Vanderbilt University School of Medicine who co-directed this research. .
The study ran from May 2020 to February 2021, before the omicron variant emerged. But Hartert said BA.5 is unlikely to eliminate allergy cross-protection.
“If something like allergic inflammation is protective, I think that would be true for all variants,” Hartert said. “The degree to which that might be protective could certainly differ.”
Avoiding infection is more difficult with BA.5
For many, the first explanation that comes to mind when thinking about avoiding Covid is their personal level of caution. tenOever believes that individual behavior, more than genetics or T cells, is the key factor. He and his family in New York are among those who have never had Covid, which he attributes to precautions like staying home and wearing masks.
“I don’t think for a second that we have anything special in our genetics that makes us resistant,” he said.
It is now common knowledge that Covid was easier to avoid before omicron, when a small percentage of infected people were responsible for the majority of the spread of the virus. A study 2020for example, found that 10-20% of those infected accounted for 80% of transmission.
But omicron and its subvariants made any social interaction more risky for everyone involved.
“It’s probably a much more even playing field with omicron variants than it ever was with previous variants,” tenOever said.
BA.5 in particular has increased the chances of people who have avoided Covid so far getting sick. President Joe Biden is a prime example: he tested positive for the first time this week.
But even so, Jha said Thursday, “I don’t believe all Americans will get infected.”