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Safety Concerns Spark Suspension Of AstraZeneca COVID-19 Vaccinations In Denmark

MARY LOUISE KELLY, HOST:

Another setback for the COVID-19 vaccine made by AstraZeneca and the University of Oxford - Denmark announced today it is temporarily halting use of that particular vaccine after several people developed blood clots. For more on the Danish decision and what else is happening with this AstraZeneca-Oxford vaccine, we're joined by NPR's Joe Palca. Howdy, Joe.

JOE PALCA, BYLINE: Hi, Mary Louise.

KELLY: All right. Can I just say up front - so before people panic, this is not one of the vaccines that people here in the states are getting, right?

PALCA: Well, I'm telling people not to panic anyway, but no.

KELLY: Yeah.

PALCA: It's not one of the authorized vaccine, although - vaccines - although it is being tested as part of a large study. But I have to emphasize, Mary Louise, that a lot of people who heard what you just said about Denmark temporarily halting the study or the rollout of the vaccine because people got blood clots are going to think, oh, my goodness. Oh, wow, this vaccine is dangerous. And I'm telling you, no, no, no, no.

KELLY: OK.

PALCA: They are investigating whether there is a relationship. People get blood clots all the time, all the time. And so you can't immediately say, oh, you got a blood clot and you had the vaccine, so the vaccine must have caused it. No, no, no, no. In fact, some people think Denmark may have jumped the gun in suspending vaccinations. John Grabenstein is a pharmacoepidemiologist who frequently advises the government on vaccine matters.

JOHN GRABENSTEIN: Stopping a vaccination program should take more than the identification of an adverse event.

PALCA: But Denmark is being cautious, and so they're going to investigate and see if there really is a connection.

KELLY: And is it just Denmark, Joe? Has this problem with blood clots and this vaccine shown up anywhere else?

PALCA: There have been reports of blood clots. This sometimes can be related. It's not certain. But the European Medicines Agency is also carrying out an investigation. But my Science Desk colleague Jason Beaubien spoke to Ian Douglas, a professor of pharmacoepidemiology at the London School of Hygiene and Tropical Medicine.

IAN DOUGLAS: In the U.K. in particular, because so many millions of people have been given the vaccine, I would expect that by now we would already have seen a signal of this problem in the U.K.

PALCA: And they don't, so...

KELLY: Yeah, they have not. OK. But I have to note - you're telling us not to panic. You're telling us this might not be linked. But the rollout of this particular vaccine, the AstraZeneca vaccine - it has not gone particularly smoothly.

PALCA: Well, no. There have been issues but not related to potential safety side effects. There have been some questions about whether there's enough data to say it works on older people, and some countries have said, we're not going to use it in our older population. It's not being used in South Africa because it doesn't appear to work terribly well against the variant that emerged down there. But it is being used widely around the world because it's available and it works and it doesn't seem to be harming people.

KELLY: Can I loop back to something you said a moment ago? You said this AstraZeneca vaccine is being tested in the U.S. What's going on with that?

PALCA: Yes, the company is hoping to get authorization to distribute the vaccine in the United States. And from the start, the Food and Drug Administration told manufacturers to get authorization. You have to do what's called a phase 3 study. That involves thousands of subjects and a well-defined protocol with certain levels of efficacy. And they'll be studying to see if the vaccine is both safe - does it have these adverse reactions? - and is it effective. And it's going to be clear, we hope, when this study is finished, which should be in a matter of weeks, whether that's true.

KELLY: All right. Thank you for keeping an eye on it. Come back when you know more. NPR science correspondent Joe Palca.

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