DEBBIE ELLIOTT, HOST:
For the first time, the Food and Drug Administration is authorizing the use of a third dose of either the Pfizer or Moderna COVID-19 vaccines, but not for everyone. Only people with weakened immune systems qualify. Joining us to talk about the FDA's decision is NPR science correspondent Joe Palca. Good morning, Joe.
JOE PALCA, BYLINE: Hi, Debbie.
ELLIOTT: So why did the FDA take this step? And who's going to benefit from it?
PALCA: Well, there's a small but growing body of evidence that some people who are immune compromised, which means they are more vulnerable to getting sick from viral or bacterial infections, will benefit from a third shot. Government officials have been talking about this lately. Here's CDC director Rochelle Walensky speaking at a briefing yesterday.
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ROCHELLE WALENSKY: Certain people who are immune compromised, such as people who have had an organ transplant and some cancer patients, may not have had an adequate immune response to just two doses of the COVID vaccine.
ELLIOTT: Joe, does this mean that people who have those conditions can just show up at their local pharmacy and get a booster shot?
PALCA: Well, it's not exactly spelled out in the FDA's announcement how people are supposed to prove to a pharmacist that they are immune compromised. But assuming they are, it would be a mistake to just run out and get a shot according to Dorry Segev. He's a transplant surgeon and researcher at the Johns Hopkins University. He's been studying these patients. And he says managing patients with weakened immune systems can be a tricky business. And only a certain subset of patients are likely to benefit from a third shot. And now Segev is trying - is doing a study sponsored by the National Institutes of Health that he hopes will clarify who are the best candidates for an extra dose of the vaccine.
DORRY SEGEV: We are planning to give 200 transplant patients booster doses under very careful monitoring to study the immune response to the booster doses and make sure that their transplanted organs are not at risk.
PALCA: And in addition to booster doses with the same vaccine or one of the mRNA vaccines, like Pfizer or Moderna, he's going to be looking at whether switching to a different kind of vaccine, like the one Johnson & Johnson makes, might work even better.
ELLIOTT: OK. Interesting. So while doctors wait for the results from that study, what is the guidance from the government about what people should do?
PALCA: Well, the CDC is going to meet - the CDC Advisory Committee on Immunization Practices is going to meet later today to talk about what circumstances are best to consider giving a third dose to and exactly to which kinds of people.
ELLIOTT: What about the question of boosters for people who don't have weakened immune systems but, say, got their vaccine six or eight months ago and are now worried that their protection might be wearing off? You know, anecdotally, we have been seeing some breakthrough cases of COVID.
PALCA: Oh, yes. Well, it's always been known that the vaccine isn't 100% protective. The president's chief medical adviser Anthony Fauci addressed that question during a White House briefing yesterday.
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ANTHONY FAUCI: Apart from the immunocompromised, we do not believe that others who are not immunocompromised need a vaccine right at this moment.
PALCA: And by vaccine there, Fauci's talking about a booster vaccine. And Fauci says it's a dynamic situation. There's a lot of studies being done, some, like the - are showing that the antibody levels, which are clearly dropping over time, might not tell the whole story. Others suggest there might be a need for a vaccine before too long.
ELLIOTT: NPR's Joe Palca. Thank you so much for the update.
PALCA: You're welcome.
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