AILSA CHANG, HOST:
The Biden administration gave the green light today to yet another COVID vaccine booster, a fourth shot. The move is aimed at shoring up waning immunity, especially as the U.S. faces the possibility of another surge. For more, NPR health correspondent Rob Stein joins us now. Hey, Rob.
ROB STEIN, BYLINE: Hey there.
CHANG: All right. So what exactly did federal health officials authorize today?
STEIN: The CDC and the FDA took a pretty sweeping step today. The FDA authorized using the Pfizer-BioNTech and Moderna vaccines as a second booster for anyone age 50 and older who got their first booster at least four months ago. And the CDC quickly recommended that. Here's the FDA's Peter Marks.
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PETER MARKS: The FDA believes that this option will help save lives and prevent severe outcomes among our highest-risk patients, which has been a top priority since the vaccines were first introduced.
STEIN: Anyone age 12 and older who has a weak immune system is eligible for the second booster, too.
CHANG: OK. And explain real quick why this would be necessary.
STEIN: Yes. So the protection people got from the first three shots has weakened with time, particularly against the omicron variant, and especially among people who are older and have other health problems. And Dr. Marks says that evidence from Israel indicates a fourth dose can pump immunity back up again.
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MARKS: If it were my relatives, I would be sending them out to do this because of the higher level of protection, because after all, COVID-19 has had a really disproportional adverse effect on people 65 years of age and older and those with comorbidities.
STEIN: Marks says the FDA picked age 50 and older because one-third of those folks have health problems that put them at risk. And older people's immunity tends to fade the fastest.
CHANG: Right. And I understand that an additional motivation for this is the new, more contagious version of the omicron variant, right?
STEIN: Yeah. Yeah. Absolutely. It's called BA.2. And it's already fueled new surges in Europe. Here's Dr. Marks again.
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MARKS: We're hoping that by taking this action, we will help allow people to take steps to protect themselves should we have another wave that comes through this country.
STEIN: In fact, the CDC released a new estimate just today that BA.2 is now the dominant strain in this country.
CHANG: God. OK. So what's been the reaction to this so far?
STEIN: You know, Ailsa, it's mixed. You know, many experts are welcoming the move. They say the vaccines are very safe, and we need to do everything possible to protect people. I talked about this with Dr. Robert Wachter at the University of California San Francisco.
ROBERT WACHTER: The evidence is very clear that immunity is waning after the first booster. And we want people to be protected against getting COVID if we can but certainly against getting severe COVID and dying from COVID.
STEIN: But, you know, not everyone is so sure about this.
CHANG: Wait. Why is that?
STEIN: Well, first of all, they just don't think the evidence is strong enough that immunity is really fading enough to warrant another shot and that a second booster would, you know, help. I talked about this with Dr. Paul Offit at the University of Pennsylvania. He advises the FDA.
PAUL OFFIT: The question is, where are the data that clearly show that those over 50 years of age benefit from a fourth dose? If there are data, I haven't seen them.
STEIN: So, you know, Offit also worries that giving people too many doses could backfire by kind of wearing out the immune system, especially if we need a new vaccine specifically targeting a variant.
OFFIT: And there's another possibility which has this sort of fancy immunological term, original antigenic sin, which just means that as you continue to give this vaccine, that you lessen the chance that you're then going to have a robust immune response when you're given a variant-specific vaccine.
STEIN: Others also worry about giving another booster too soon and any immunity people get wearing off before another surge hits. It's also unclear just how much demand there will be for a second booster, given how few have gotten the first.
CHANG: That is NPR's Rob Stein. Thank you, Rob.
STEIN: You bet. Transcript provided by NPR, Copyright NPR.
