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New study finds a genetic variant may explain why some get COVID but have no symptoms


Some people catch COVID-19 but get no symptoms. A new study finds a genetic mutation may explain why. Here to tell us more is study co-author Jill Hollenbach, a professor of neurology and epidemiology at UC San Francisco. Good morning and welcome to the program.

JILL HOLLENBACH: Good morning. Good to be here.

FADEL: So I think a lot of people who just heard me describe this genetic mutation might wonder, how do I get that? I mean, how many people have this genetic variant? And why does it keep them from getting sick when they contract COVID?

HOLLENBACH: Yeah, so this is a relatively common variant of a set of genes called HLA. And just for some context, those are the genes that we talk about when we talk about matching for transplants. So there's a lot of different versions of these genes. They vary from population to population. But in individuals with European ancestry, we see this particular version that we identified in our study in about 10% of people. It varies between ancestral groups.

FADEL: And what do you mean it varies between ancestral groups?

HOLLENBACH: I mean, given your ancestry, you may be more or less likely to have this particular variant. So we find that in different populations anywhere from two to maybe 12% of the population.

FADEL: And how does it protect people from COVID symptoms?

HOLLENBACH: Yeah, well, what we think is that people are protected through some preexisting immunity that they have from prior exposure to seasonal cold viruses. So there's a lot of coronaviruses, and some of them cause what we all experience as mild seasonal colds. And some of those are - share a lot of similarities with SARS-CoV-2, the virus that causes COVID-19. And we think that, for whatever reason, these individuals that have this particular variant of HLA form particularly good immunity towards these colds. It's very effective at dealing with the SARS-CoV-2 virus when they encounter it. So it's kind of like having an army of immune cells that are primed and ready to attack as soon as the virus infects them.

FADEL: That sounds great. How do you find out if you do have that variant?

HOLLENBACH: Well, it's not something that you would normally find out unless, for example, you were going to be a volunteer bone marrow donor or you were being tested for some kind of medical necessity. We're not necessarily recommending that people go looking to find out whether they have this variant because it doesn't ensure that you're going to be asymptomatic. It just makes you much more likely to be so.

FADEL: Right. And so why does it matter to know that this exists? How could the findings be used in COVID treatment, vaccine research?

HOLLENBACH: You know, I think that, from a fundamental point of view, understanding what genetic and immunological conditions gives people an upper hand, in terms of managing infection to the point that they don't even experience any symptoms, gives us a lot of clues about what are the necessary, you know, conditions needed to have that kind of outcome. We're hoping that this can help us to design a more precision medicine-oriented kind of approach to vaccines, and in particular, gives us an opportunity to think about whether, you know, a goal for vaccination might be absence of symptoms as opposed to the absence of infection.

FADEL: Jill Hollenbach, a professor of neurology and epidemiology at UC San Francisco. Thank you for your time.

HOLLENBACH: Yeah, thanks so much for having me. Transcript provided by NPR, Copyright NPR.

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Leila Fadel is a national correspondent for NPR based in Los Angeles, covering issues of culture, diversity, and race.