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Scientists Are Working On Booster Shots In Case COVID-19 Vaccines Lose Their Effect

MARY LOUISE KELLY, HOST:

The COVID vaccines available in the United States today work extremely well at preventing illness, but there are still questions about how long that protection will last and whether they'll work against viral variants that could pop up. So, as NPR's Joe Palca reports, researchers are coming up with strategies for boosting the existing vaccines.

JOE PALCA, BYLINE: The current crop of COVID vaccines work by prompting people's immune systems to make antibodies to the virus so they can fight it off if they're ever exposed to it. Virologist Mark Denison of Vanderbilt University says usually the levels of antibodies made this way will decline over time, reducing the protection vaccination provides. That is happening with the COVID vaccines.

MARK DENISON: I'm frankly really impressed with how slowly the antibody levels are declining and that there may be protection at levels that are lower than we would have expected or hoped for so that even though they're declining, it doesn't mean that we're unprotected.

PALCA: That's the good news. But they are still declining, and eventually the protection from the vaccine may expire. Even though we're not there yet, it's prudent to prepare. Another challenge is mutations in a key virus component called the spike protein. That can lead to variants of the virus that existing vaccines won't make the right antibodies to. Denison says you can deal with both possibilities by using boosters.

DENISON: What boosters would do would be to present the new version of the virus spike, which may amplify the ones we already have and broaden the types of antibodies we have.

PALCA: But before you can make a booster that can deal with a new variant, there are certain critical things you need to know.

NADINE ROUPHAEL: One is understanding what variant are we dealing with.

PALCA: Nadine Rouphael is director of the Hope Clinic of Emory Vaccine Center. She says it doesn't make sense to give people in the United States a vaccine designed for, say, the South African variant if that variant isn't circulating here. And in some cases, it may be enough to simply boost antibody levels with the original vaccine. Higher antibody levels may be able to deal with most, if not all, variants. She's testing both possibilities using a new vaccine made by Moderna.

ROUPHAEL: Either a boost that's the original vaccine, either a boost that's the variant vaccine or a mixture of both.

PALCA: If researchers determine a new vaccine is needed to deal with a new variant, there's a big question. How will the Food and Drug Administration decide what kind of testing is needed to show the new vaccine is safe and effective? The current crop of vaccines were tested using large studies involving tens of thousands of people to see if the vaccine really prevented COVID disease. That takes too long if a new vaccine is needed urgently. Peter Gilbert of the Fred Hutchinson Cancer Research Center is leading an effort to test vaccines using a blood sample.

PETER GILBERT: A blood sample that can be used to reliably predict that the vaccine prevents COVID without needing to measure whether a person goes on to get COVID.

PALCA: Gilbert says the blood test could be ready in a matter of weeks. Vanderbilt's Mark Denison says you shouldn't think because a booster may be necessary, vaccines aren't an effective tool for dealing with the COVID pandemic.

DENISON: I'm just fine with a booster if that's what's needed because I think it reflects the reality of the biology. This isn't fairyland. This isn't magic. It's real biology.

PALCA: Denison says you can think of the COVID pandemic as a chess game - humanity versus the virus. By mutating into new forms, the virus may be able to break away from our human attempts to keep it in check.

DENISON: It's showing us that it has chess moves ready. It has chess moves to do still. But we have chess moves left, too.

PALCA: And to maintain the chess analogy, we could be in for a long endgame. Joe Palca, NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.