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Preliminary Results Show AstraZeneca Vaccine Can Prevent COVID-19


A coronavirus vaccine that is currently being used all over the world might also be available soon in the U.S. AstraZeneca announced preliminary results today from a study of its vaccine that involved 32,000 volunteers. The FDA requires studies like this before it will grant emergency use authorization. Now, there have been some concerns about this particular vaccine. Dozens of countries temporarily stopped giving it after a very small number of recipients developed blood clots. NPR science correspondent Joe Palca is covering this one. Good morning, Joe.

JOE PALCA, BYLINE: Good morning, Noel.

KING: How well did the vaccine do in this study?

PALCA: Actually, quite well. This was a study of, as you said, about 32,000 people. Two-thirds got two shots of the vaccine spaced four weeks apart, and one-third got two shots of a placebo. And they compared the efficacy of the vaccine - 79% percent were protected from getting COVID-19, which is good. A hundred percent were prevented from getting severe disease and hospitalization. And these results are kind of interesting because earlier studies that the company had reported on had much more variable results - and somewhat lower, in fact, in many circumstances. So good news.

KING: Good news. How does it compare to the other vaccines that are out there?

PALCA: Well, not bad. You probably remember Moderna and Pfizer. Those were the first two vaccines to come out - mRNA vaccines. They were reporting 90% to 95% efficacy. Johnson & Johnson, which is a vaccine very similar to the AstraZeneca one, was closer to 70% efficacy. So it was somewhat better than that, although the Johnson & Johnson vaccine only requires a single dose, which makes it desirable for public health reasons - easier to get to people.

This study didn't answer the question of whether the AstraZeneca vaccine will work against some of the new variants that are circulating. It was completed in the United States before the U.K. variants started circulating widely in this country. And other studies have shown it doesn't appear to work so well against the variant circulating in South Africa. So still a question mark there.

KING: OK. And the variants, of course, as you've reported - a very big deal. Did this study find any evidence that people who took this vaccine developed blood clots, which was the reason that some European countries temporarily stopped giving it?

PALCA: Yeah. They - the company, in the press release they put out this morning, was very specific about saying they looked for any indication of this in the 21,000 or so people who got the vaccine, and they did not see any. But I should point out that this is a study of, as we say, 20,000 people got the vaccine and the signal - if this is a rare event that only occurs once in 100,000, once in a million, once in 10 million people, you simply won't see it in a study of 21,000 people. So it may be there; it may not.

KING: OK. And when will the FDA make a decision about the AstraZeneca vaccine?

PALCA: Well, the company says it's, you know, sending its paperwork to the FDA. The FDA will then go through a very detailed look at it, going down to the very individual cases in some cases to make sure that its analysis agrees with AstraZeneca's analysis. Then there's an advisory committee meeting, and then there's a decision. So all that could come in the next weeks or month.

KING: OK. NPR's Joe Palca. Thanks, Joe.

PALCA: You're welcome. Transcript provided by NPR, Copyright NPR.

Joe Palca is a science correspondent for NPR. Since joining NPR in 1992, Palca has covered a range of science topics — everything from biomedical research to astronomy. He is currently focused on the eponymous series, "Joe's Big Idea." Stories in the series explore the minds and motivations of scientists and inventors. Palca is also the founder of NPR Scicommers – A science communication collective.