LEILA FADEL, HOST:
The flu shot is different this year. The vaccine will be missing a strain of influenza it's protected against for more than a decade, and that's because that strain has likely gone extinct, thanks to COVID-19. Health and science reporter Sarah Boden explains.
SARAH BODEN, BYLINE: Back in 2020, the COVID virus managed to spread to every corner of the world despite all the isolation and masking. An unintended consequence of that strange, lonely year is a strain of flu known as B/Yamagata seems to have disappeared.
KEVIN R MCCARTHY: Early - midway through 2020, people were realizing that you weren't seeing sequences. And I didn't believe it at first, and I don't think a lot of people believed it.
BODEN: Kevin R. McCarthy studies the coevolution of viruses at the University of Pittsburgh's Center for Vaccine Research. He says what happened with B/Yamagata was a big surprise. And if it is truly gone, this will be the first documented instance of a virus going extinct simply because people stayed away from each other. So social distancing can stamp out a virus, just not COVID. Now, there were a couple of things working against B/Yamagata. For one, the strain of flu hasn't been around for decades, so there was population immunity. Also, it was in competition with another flu virus.
MCCARTHY: So the B/Yamagata strain co-circulates with sort of its twin, B/Victoria. And for the past few years, the Victoria lineage was winning the battle of global domination.
BODEN: Since B/Yamagata hasn't been seen for years, the Food and Drug Administration said it's time to pull it from the annual flu shot. That's the right call, says Kawsar Talaat, an infectious disease physician at Johns Hopkins Bloomberg School of Public Health.
KAWSAR TALAAT: If you include a strain for which you don't think anybody's going to get infected into a vaccine, there are some potential risks and no potential benefits.
BODEN: ...Even if those risks are infinitesimally small. The absence of B/Yamagata won't change the experience of getting this year's flu shot, and unvaccinated people are no less likely to get sick. Other strains of influenza are still circulating, and thousands of Americans die every year because of it. But Talaat says this change to the vaccine simplifies manufacturing, which makes it easier to produce more doses. And that's good for everyone.
For NPR News, I'm Sarah Boden. Transcript provided by NPR, Copyright NPR.
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