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The Latest On International COVID-19 Vaccine Development Efforts

ARI SHAPIRO, HOST:

We're all counting on the COVID-19 vaccine to help end the coronavirus pandemic. But recently, new, more infectious versions of the virus have been showing up around the world, raising questions about how well the existing vaccines will work against these variants. Today, vaccine maker Moderna announced its vaccine does seem to work against at least two of the new variants. Joining us to talk about this is NPR science correspondent Joe Palca.

Hi, Joe.

JOE PALCA, BYLINE: Hi, Ari.

SHAPIRO: How did Moderna test its vaccine against these new variants?

PALCA: Well, it took blood from people who had already been vaccinated and then mixed that blood with a synthetic version of the viruses that are popping up. And as you - they said they're particularly interested in the variants that were first seen in the U.K. and South Africa - these seem to be especially infectious - and then look to see whether there were antibodies in the blood of these people who had been vaccinated that can neutralize the virus - that is, prevent it from infecting cells.

And the vaccines worked - I mean, meaning the antibodies in the blood of people vaccinated could neutralize the virus. But in the case of the variant originating in South Africa, the vaccine - the blood didn't do as good a job at neutralizing it - good enough, they think, to protect someone, but not as good.

SHAPIRO: And so what does that mean in terms of people's fears about the vaccines failing against these new strains?

PALCA: Well, it basically means that people have to be aware that it's possible that this won't work exactly as advertised. Now, these - was a small study. It doesn't guarantee success or failure at this point, but it's encouraging, at least for now, to know that there is some indication, at least, that the vaccines are working.

SHAPIRO: And is there a plan of attack if the vaccine turns out not to work as effectively?

PALCA: Well, yes. I mean, Moderna announced today that they would be developing a new version of its vaccine. It's modifying it so that it's specifically targeted at the variant that first emerged from South Africa. I spoke with John Mellors, chief of infectious diseases at UPMC in Pittsburgh. And Mellors says the - Moderna is doing the right thing, taking steps now to make a modified vaccine.

JOHN MELLORS: If we don't need it, fine. If we need it and don't have it, not fine, not good.

PALCA: So the good news is that it's relatively easy to modify an mRNA vaccine. That's the kind of vaccine that Pfizer and Moderna are making. So making the modified vaccine shouldn't be a Herculean task.

SHAPIRO: OK. And in other vaccine news, the pharmaceutical giant Merck today announced it's abandoning the two COVID-19 vaccines that it was developing. Why did they do that?

PALCA: Well, they had started to test their vaccines on a small number of people, and they just weren't getting the kinds of results that they were hoping for. These were different vaccines from the Moderna and Pfizer vaccines. Those are mRNA vaccines, as I mentioned. And Merck was doing what's known as a viral vector vaccine. And the thing is they used this technique successfully to make an Ebola vaccine that worked. So I said, well, OK - I asked John Mellors why, well, if they work for Ebola, why this approach didn't work for the coronavirus.

MELLORS: The biology is complicated, and it doesn't always work according to plan. And we don't totally understand why.

PALCA: So he says scientists have learned a lot about the coronavirus in the past year, but there's still a lot they don't know.

SHAPIRO: That's NPR science correspondent Joe Palca with the latest on the COVID-19 vaccines.

Thanks, Joe.

PALCA: You bet. Transcript provided by NPR, Copyright NPR.