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Certain Strains Of Flu May Have Gone Extinct Because Of Pandemic Safety Measures

ARI SHAPIRO, HOST:

Here's an unexpected upside to the pandemic. For more than a year, we've masked up limited social interactions, skipped vacations. Those efforts were meant to keep the coronavirus at bay. And now scientists say those actions also may have driven certain strains of the flu to extinction. That could make it much easier to develop flu vaccines in the coming years. Helen Branswell wrote about this for STAT and joins us now. Welcome.

HELEN BRANSWELL: Hi, Ari.

SHAPIRO: To start with some background, remind us. The flu is not just one type of virus. There are multiple strains.

BRANSWELL: That's right. You know, your listeners may know that every year when they get a flu shot that it protects against three or four different strains of flu. There's H1N1, which they'll know from the 2009 pandemic. There's H3N2. And there are two components that protect against influenza B viruses - B/Victoria and B/Yamagata.

SHAPIRO: And so I guess each year the people who develop flu vaccines sort of have to - I don't know - make an educated guess about which strains are going to be circulating that year. And if they're wrong - I mean, you report that in a recent year, up to three quarters of people who got the shot actually were not immunized against the flu.

BRANSWELL: Yeah. So what they have to do is sort of look within each class of viruses to see which strains are the most dominant. But they're doing it months in advance. Like, for our flu shot in the Northern Hemisphere, they're deciding in February what should go into the flu shot we're going to get the following autumn. So they have to look and see what seems to be dominant, what seems to be receding and make some choices. But it's been very hard in recent years, particularly with H3N2 viruses because they've been so diverse. And knowing which is going to be the dominant strain the next winter has been really tough. But it now seems like, you know, the diversity has been diminished because there's been so little circulation of the viruses.

SHAPIRO: So how does a strain of the flu go extinct?

BRANSWELL: Well, they have to continue to infect people, or they won't - you know, they don't just sort of live out there. They have to pass from person to person to continue to exist. And because of the measures we've been taking in the pandemic - the distancing, the masking, closing of schools would be big because kids are major amplifiers of flu. But another thing that will have had a big effect on this will be the huge reduction in international travel. You know, flu moves from the Southern Hemisphere in their winter and our summer to the Northern Hemisphere when it's our flu season. And that just doesn't seem to have been happening to the degree that it normally does. And as a consequence, there are just fewer of these viruses around.

SHAPIRO: So what does that mean for developing a vaccine?

BRANSWELL: Well, it's early at this point. You know, the scientists who are looking at this are really interested. And they're hoping that some of these strains have gone extinct, but it's still early days. I mean, they're going to have to watch that for a while to feel confident that they really are gone.

SHAPIRO: Does this finding suggest that maybe even after this pandemic is over, people should consider wearing masks and taking some of the other health precautions we've gotten used to, especially during cold and flu season?

BRANSWELL: You know, I think there are going to be a lot of people who are going to think about that. You know, some of the precautions that we've taken to suppress COVID are not sustainable or desirable.

SHAPIRO: Sure. We're not going to keep schools closed.

BRANSWELL: Exactly. We're not keeping schools closed. International travel will return eventually. So some of these things will fall away and should fall away. Now, you know, should people who aren't feeling well next winter stay home from work? Probably. Should people who have sick kids keep them home from school? Definitely. And should people be thinking about wearing a mask? You know, I think that will depend on an individual's level of comfort. I mean, clearly, there are people who can't wait to doff their masks, and there are others who are hesitant about it. So I think we'll probably see a mix going forward.

SHAPIRO: Helen Branswell is a senior writer at STAT covering infectious diseases and global health. Thanks for your reporting.

BRANSWELL: Nice to talk to you. Transcript provided by NPR, Copyright NPR.