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Scientists are starting to understand the likely endgame for COVID-19

STEVE INSKEEP, HOST:

What is the end game for COVID? We seem to have made it past the worst of the delta surge. Case levels are less than half what they were a couple of months ago. We've reported on this program on projections that new cases may keep dropping all winter. But of course, that is just a projection, and it does not answer how the pandemic would completely end, if it ever does.

NPR global health correspondent Michaeleen Doucleff has been asking, what happens next? Michaeleen, good morning.

MICHAELEEN DOUCLEFF, BYLINE: Good morning, Steve.

INSKEEP: Let me just start by asking, can we hope for a time when the coronavirus is effectively gone from the world the way that polio and smallpox were all but eliminated?

DOUCLEFF: So that works when the virus is very stable over time - right? - its genetic sequence doesn't mutate much, like the measles. So when you get a vaccine, it can protect for a long time. But not all viruses are like that. For instance, the flu, it mutates really rapidly. And those mutations can decrease the vaccine's effectiveness. And that's one reason why you can get reinfected over and over again with the flu. So it really depends on how fast SARS-CoV-2 is mutating.

INSKEEP: OK. How quickly is that happening?

DOUCLEFF: Well, at first, during the first year of the pandemic, it looked good. It was mutating very slowly. And then in December last year, right around the holidays - remember? - that's when everything changed.

(SOUNDBITE OF MONTAGE)

BILL WOLFF: This is NBC Nightly News.

LESTER HOLT: Tonight, the race to stop a new, highly contagious strain of coronavirus.

UNIDENTIFIED ANCHOR #1: Tonight, London on lockdown - scientists there believe that this variant...

UNIDENTIFIED ANCHOR #2: More countries are detecting that new, highly contagious variant of the disease.

INSKEEP: You know, when this was happening, when the news was breaking, it sort of made intuitive sense to me because I knew that it had infected so many millions of people that the virus had many chances to evolve.

DOUCLEFF: Yeah, that's right. In South Africa, the U.K., Brazil, all of the sudden it looked like SARS-CoV-2 was mutating a lot. Recently, scientists at the University of Washington developed a new method to measure how quickly it's mutating or evolving. Katie Kistler was part of that study. And she says she was surprised at how fast this virus is changing.

KATIE KISTLER: Late in 2020, that evolution really starts picking up to a rate that's, like, remarkably, like, high right now - roughly four times higher for SARS-CoV-2 than it is for seasonal flu.

DOUCLEFF: And remember, the flu changes so fast that people can be vulnerable to it each year. So right now SARS-CoV-2 is changing four times faster than the flu.

INSKEEP: Wow. Does that mean that COVID is going to just keep coming back and back and back in different versions the way the flu does?

DOUCLEFF: That's the leading hypothesis right now. I was talking to Dr. Abraar Karan at Stanford University about it. He's an infectious disease specialist. He says exposure to this virus will be essentially unavoidable.

ABRAAR KARAN: So I think that everyone will be exposed to SARS-CoV-2 the virus. It's a matter of when that will be. And another question is whether you're exposed when you're fully vaccinated or when you're not vaccinated.

DOUCLEFF: So now, Steve, this is key. The virus SARS-CoV-2 will probably never go away. But as Karan pointed out to me, COVID the disease, the extreme illness that puts many people in the hospital, that could go away. And here's why. COVID is caused by a type of coronavirus. And the U.S. has dealt with many coronavirus outbreaks in the past. I'm talking about huge outbreaks year after year for decades. And people have hardly noticed them. I surely haven't noticed, have you?

INSKEEP: I hadn't, no.

DOUCLEFF: No. And that's because these other coronaviruses typically cause just a mild cold. So there are four of them. And every year, one or more of them sweeps through the country - through schools, churches, offices - and makes people sick.

Rachel Eguia is a biologist at Fred Hutchinson Cancer Research Center. She says that throughout your lifetime, you've likely caught these viruses perhaps a dozen times.

RACHEL EGUIA: It definitely is known that every few years you're able to get reinfected with them. And so we were wondering, is that the same story for, you know, this new coronavirus, this SARS-CoV-2?

INSKEEP: I think I'm beginning to get this. The realistic hope here is not that the virus vanishes from the Earth but that we moderate its effects.

DOUCLEFF: Yeah. That's exactly right. And some scientists are starting to think that eventually, over time, COVID may turn into something similar to a type of disease like these other coronaviruses - a seasonal cold or a flu-like illness.

Rustom Antia is one of the scientists that thinks that. He's a computational biologist at Emory University. And for the past year and a half, he and his colleagues have been using data from these other coronaviruses to try and predict how COVID will behave in the long run.

INSKEEP: OK. What's his best prediction?

DOUCLEFF: He thinks that COVID will become a flu-like illness if two things happen. First, immunity to severe disease has to last a long time. So after some level of exposure - a few natural infections or two or three doses of the vaccine - you might still be able to get infected, but you aren't likely to get really sick and end up in the hospital.

INSKEEP: OK. So it depends on our bodies, in effect. Do we know if our immunity will protect us for a long time whether we got it from an infection or from the vaccine?

DOUCLEFF: Yeah. That's what everyone is anxiously waiting to see. After the vaccine, so far, immunity looks like it's holding up for at least six months or so for healthy adults. But Antia says right now it's unclear how long that critical immunity will last for people more at risk for severe disease.

RUSTOM ANTIA: What we don't know just now is for older individuals, like I am, and older people, how many times we'll need to be vaccinated for the vaccine to build up our immunity so that when we do get infected naturally, it's not severe.

DOUCLEFF: So with that long-lasting immunity, the vast majority of the population would, in theory, be protected against severe COVID. And that would really leave only one population unexposed. Can you guess which one that is?

INSKEEP: Brand-new people - newborns.

DOUCLEFF: Yes, exactly - young children. But remember, Steve, so far, COVID is relatively mild in kids. And as long as it stays that way, kids can get infected early on when they're young, build up their immunity and then have protections from severe disease as adults. So in theory, everyone around the world would be protected. Now, the buildup of this immunity across, you know, the whole population can take a long time. We're talking perhaps years. And that's why it's so important for people to get vaccinated because that can speed up this process and more quickly turn COVID into a disease that looks possibly like a mild flu or even a common cold.

INSKEEP: Hey, Michaeleen, thanks for this glimpse at what might be - could be our future - really appreciate it.

DOUCLEFF: Thank you so much, Steve.

INSKEEP: That's NPR global health correspondent Michaeleen Doucleff. Transcript provided by NPR, Copyright NPR.