DANIELLE KURTZLEBEN, HOST:

The number of COVID-19 cases in the United States as a whole has been on the decline in recent weeks, and in many places, mask mandates and other restrictions are being dropped. But at the same time, a new COVID variant has been spreading across the country. BA.2 is a subvariant of omicron, the variant behind the biggest spike yet of the pandemic just a couple of months ago. So how should we be thinking about COVID as we enter yet another new phase in the pandemic? To help us answer that, we called Bill Hanage. He's an epidemiologist and a professor at Harvard's T.H. Chan School of Public Health. Dr. Hanage, welcome.

BILL HANAGE: Thanks for having me on the show.

KURTZLEBEN: Of course. So first of all, let's start with some basics. Tell us more about this BA.2 variant. How does it differ from the original omicron variant? And is it more contagious? Does it cause more severe illness?

HANAGE: Well, the first thing to remember is that BA.2 is a different subvariant of BA.1, which is the original omicron. They're both omicron. It's just they're different flavors of it. But BA.2 is actually quite divergent from the virus that was causing a lot of disease here a couple months ago. It's very different indeed. We don't really understand where these two came from. My own bet is on a long-term infection in an immunocompromised host. But because BA.2 is really quite different, we have to be watching it very closely because we are still learning about its epidemiological properties. And among those properties, it does appear to be more transmissible, even more transmissible than the omicron that we've seen to date.

KURTZLEBEN: I want to bring this down to the individual level because there are a lot of people listening who have had their two vaccination shots plus a booster, but they got that last shot, at this point, several months ago. So should those people be more worried as we have this new variant moving among us and as there's the potential for booster effectiveness to wane?

HANAGE: The booster effectiveness certainly does seem to wane against infection. It seems to be pretty well preserved against severe illness. Now, I want to put a small caveat on that, which is that because things are changing very, very quickly, we might be waiting a couple of weeks to actually get really secure data on this. But right now, it doesn't look like BA.2 is much more serious in terms of the disease it causes. than BA.1 But the best thing that you can do as an individual, and in particular if you're over 65 years of age, is to make sure that you're fully up to date with your shots, that you've been boosted. That's the very best thing that you can do in the face of a virus like this.

KURTZLEBEN: One more thing I want to ask about boosters - what do you think about the reports that the Biden administration might be considering approving additional boosters for people over 50 or just for the population in general?

HANAGE: I think that a fourth booster is probably on the cards and probably on the cards for people who are - who really need it, who are going to be the older folks. Even beyond BA.2, we can expect that there's going to be more virus in the fall and the winter. And because those people might have immunity that has waned a little bit, we might want to give it a bit of a fill-up in order to help it get through another difficult period of the virus. For people as a whole, in general, I think that three shots is probably about as much protection as you're likely to get. But as I say, check back with me in a few months.

KURTZLEBEN: And sort of along those same lines, people who are more vulnerable or immunocompromised people, does BA.2 make you think that perhaps we should be taking more precautions on their behalf?

HANAGE: I think that that's certainly true, that we should not forget that there are a lot of people in the United States who have conditions that predispose them to more serious infection if they become infected. And if you see a very large surge coming into your community, then certainly you should think about your neighbors because even though you might be cool with being infected, they might not be. And so this is something which - you know, you're looking out for your community.

KURTZLEBEN: Well, that brings me perfectly to one other thing I wanted to ask you because, you know, many states, businesses, workplaces across the country are relaxing their mask mandates, relaxing restrictions that have been in effect for quite a while. I'm wondering, what is your advice to people listening? How - should they keep wearing their masks? What kind of precautions should they be taking?

HANAGE: I think it depends on the situation that you are in and depends on how much virus there is in the community at the time. You know, if there is very little infection, then wearing a mask in a lot of circumstances may not be particularly helpful unless, that is, of course, you're in a particular group who's very concerned about infection. And you can have one-way masking. KF-94s and N95s are very good, and people may want to use them because they don't want to get infected. And there's a lot of reason people might not want to get infected. They might not want to be having - missing their vacation which is coming up, just for example.

So it's roughly the same message as it has always been. Look at what's going on outside your front door. How much viruses are in the community? What are the consequences of you or somebody you're in contact with getting sick? Are they in a vulnerable group? Is it something they can do to wear a mask, which is a really easy thing to do? Seriously, are you really going to the grocery store to feel the fresh air on your face, or are you going onto public transport to feel the fresh air on your face?

I understand that these are things that people can feel - you know, people have different attitudes to. But then what you can do is make the contacts that you do make the special ones, the important ones, the things that really matter to you. And those things, we can get much, much of that back, even in the face of a virus like this.

KURTZLEBEN: To wrap this all together, a final, really big question - what do you think comes next in this pandemic?

HANAGE: Right now, BA.2 is becoming the majority of the virus population in the U.S. What that means is that we're going to see a bump in infections. How large that bump is going to be, well, that depends on how much people are trying to stop it. It depends on how many people have some immunity already because they were infected with BA.1. It also depends on - in terms of its consequences, on how many people are vaccinated and boosted. The United States is not very well vaccinated and boosted. The U.K. rode out its early omicron wave really quite well. We cannot say the same for the U.S. Between two and three times as many people, corrected for population, lost their lives. You really should be boosted.

KURTZLEBEN: That was Bill Hanage, associate professor of epidemiology at Harvard's T.H. Chan School of Public Health. Dr. Hanage, thank you so much for speaking with us today.

HANAGE: Thanks for having me. Transcript provided by NPR, Copyright NPR.