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What The Heck Is Going On With AstraZeneca’s COVID-19 Vaccine?

The AstraZeneca COVID-19 vaccine has been hailed as the world’s vaccine — it’s inexpensive to produce and doesn’t need super-cold storage like the mRNA vaccines do. It’s been approved in countries around the globe, from the U.K. to Mexico to Australia

At first, clinical trial data indicated that the vaccine had an efficacy of nearly 80 percent, though a small study of about 2,000 people showed it to be considerably less effective against the variant first identified in South Africa. But that hasn’t been seen as a reason to keep the vaccine from the rest of the world. And so far, tens of millions of doses have been administered.

Nevertheless, the vaccine has still not been approved in the U.S. This week, on the verge of submitting their vaccine for FDA approval, AstraZeneca committed essentially a communications faux pas that could shake the public’s confidence in the shot. And, unfortunately, it’s not the first public relations scandal AstraZeneca has gotten itself into since the pandemic began. 

On this week’s episode of PODCAST-19, we explore AstraZeneca’s missteps and what to make of them with Maggie Koerth, FiveThirtyEight’s senior science writer. You can find the transcript below.

Anna Rothschild: Maggie, what the heck is going on with AstraZeneca?

Maggie Koerth: What the heck isn’t going on with AstraZeneca? So, this is still a little confusing. And I think part of what is making it confusing is the communication around it. So what seems to be going on is that AstraZeneca had this big press conference; they released efficacy data that was based on data from one period of time. So they came out and said, “You know, we’re going to have an efficacy of 79 percent.” That’s great. But then the Data [and] Safety Monitoring Board, which is the regulator in charge of all of this, is saying that if you add in this extra time period that they have data for, but that they just kind of left out in the public announcement, you’re actually going to get an efficacy of closer to 69 to 75 percent.

Anna Rothschild: Basically, when you do a clinical trial, right, you have this, like, impartial board called the Data [and] Safety Monitoring Board that sees your data before even, like, the CEO of the pharmaceutical company sees the data. In this case, pretty much back in February, the Data Safety [and] Monitoring Board found that there was an efficacy rate in the most recent clinical trials at AstraZeneca of like 79 percent. But there were these, like, additional potential cases of COVID that they kind of wanted AstraZeneca to look into. So, AstraZeneca kind of looked into some of them. And by March, that number dropped to 75 percent. But there were still, according to this [Washington] Post article I read, like 33 potential cases of COVID that could bring that number down to 69 percent. And basically, like, the regulatory board (again, which is not related to AstraZeneca at all — they are an impartial board) told AstraZeneca these numbers, but were like, “Listen, you really got to check this out because these numbers could change.” And then AstraZeneca just decided to go with the February numbers, knowing that there was this potential change in what could occur. Then this regulatory board did a thing that is — you almost never hear this happen in public health: Like, they basically, like, wrote to AstraZeneca that they were very disappointed in them and that this had the potential to mislead them and then freakin’ cc’d Dr. Fauci on it.

Maggie Koerth: Oh, I didn’t know they cc’d him on it. Oh, wow. Oh my gosh. That’s … that’s some … that’s some like, please see my previous email.

Anna Rothschild: I know!

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Maggie Koerth: And what is absolutely driving me completely bonkers is that we’re having this whole thing over a less than 10 percent difference in efficacy. Like, there’s this massive loss of trust involved in this communication. These are really weird things to be happening. And it’s less than 10 percent difference.

Anna Rothschild: I think that that’s kind of the most galling thing, too. There’s just something so weird going on about the fact that they really wanted to release the 79 percent number, when in fact, it might have been 75 percent effective. And the difference between those numbers is fairly small.

Quick side note here: We recorded this episode on Wednesday afternoon. That night, AstraZeneca released an update saying that after a review, they’ve now determined that their vaccine has a 76 percent efficacy against symptomatic COVID, and 100 percent efficacy against hospitalizations and deaths.

Maggie Koerth: It just seems like there’s been a lot of this stuff all the way along with AstraZeneca.

Anna Rothschild: Well, let’s talk about some of these other scandals.

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Maggie Koerth: So, what I kind of have seen in going back and looking through a lot of this stuff is this pattern of, like, both choosing the more optimistic thing to talk to the press about, and also this pattern of just kind of methodological sloppiness. They wanted to combine all of these different studies that they had been doing all over the world that were done differently, with different doses — and in different ways — into one big meta-analysis. That’s not a thing — like, we don’t do that. 

Anna Rothschild: Didn’t they also give some study participants a half dose of the vaccine accidentally at some point?

Maggie Koerth: Yeah. When they were releasing some of their data, you had, like, this result, where like, oh, a half dose, and then a full dose gets you a better effectiveness rate than two full doses. And so the press kind of got curious about that. And like, “What even made you try this?” And it turned out that what made them try that was a complete and utter accident that happened when one of their contractors was giving the wrong dose out in one trial. 

Anna Rothschild: Jeez.

Maggie Koerth: It’s not like they were hiding it from the regulators. Like, the regulators knew. But they had not made it clear in the public-facing data. So you just had this, like, weird hanging question that then they had to explain that that made them look like they were hiding things. The PR failure has also been going on for quite a while. 

Anna Rothschild: Oh, absolutely. I don’t know if you remember, like, earlier on in their clinical trials there were, like, one or two cases of this, like, super-rare paralytic condition called transverse myelitis, which we talked about on PODCAST-19 before, and basically, like, the trials were stopped. The crazy thing, though, is that the way that the FDA found out about the case of transverse myelitis was the same way the public found out, which was through a leaked story to, I think, STAT News.

Maggie Koerth: Oh, god, I’d forgotten about that.

Anna Rothschild: It was later found that there was no link between the vaccine and transverse myelitis. This is actually just, like, a thing that these two people in these very large studies happened to develop that, in all likelihood, had nothing to do with the vaccine whatsoever. But the fact that it was communicated so poorly just makes you go, “Wait, are you hiding something?”

Maggie Koerth: Right. And you also have things that are, like, not scandals per se, but like, do you remember what was going on with, like, the whole, “This doesn’t work in old people” thing? 

Anna Rothschild: Oh, yeah. I mean, I think what happened was that AstraZeneca, like, they didn’t do an excellent job of recruiting enough older people in the study, people over 65 in their study. And so that kind of got misconstrued by the public. And I think, famously, [by] Emmanuel Macron. 

Maggie Koerth: Right.

Anna Rothschild: By interpreting that as, “Oh, this vaccine doesn’t work in people over 65,” that’s not necessarily the case.

Maggie Koerth: It seems to be working right in people over 65 in the U.K., for instance.

Anna Rothschild: Exactly, exactly. In reality, we just didn’t have enough data to say whether the vaccine worked in people over 65 at the time.

Maggie Koerth: Right? So it’s another one of those cases of where, like, it’s not that they’re evil. It’s just that they’re, like, walking into walls repeatedly.

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Anna Rothschild: Another quick side note: In their Wednesday night press release, AstraZeneca said their vaccine has an 85 percent efficacy in people 65 and older.

Maggie Koerth: And I think, like, some of the communication around this has also been … it’s not all on AstraZeneca. Like, you get into, like, the blood-clotting thing. And that communication has been bad from, like, everybody basically.

Anna Rothschild: Well, let’s talk about that. What did happen with the blood clots? 

Maggie Koerth: So, there are at least 21 countries that put a temporary pause on using the AstraZeneca vaccine. So, what is going on is that there are at least 30 cases of not just blood clots, but severe blood clotting, and a syndrome of different symptoms. You know, some people are having head-to-toe blood clots, some people are having these low platelet counts. Nobody knows whether this is tied to the vaccine. Nobody knows why it would be heavily centered in Germany, where there’s been at least 13 cases. But it’s the kind of thing that if you’re a vaccine safety expert, you’re looking at this information and you’re thinking, “Let’s, let’s hold up a minute and find out what’s going on.” But if you’re a public health person, you’re looking at this exact same information and you’re going, “But it’s just 30 cases, and there’s been tens of millions of doses of this stuff given out. So you’re still way more likely to die from COVID.” So let’s prioritize getting people vaccinated. It’s really just this clash between how two different expert groups prioritize the same thing.

Anna Rothschild: Basically, like, the European Medicines Agency has said that the benefits of the vaccine continue to, like, far outweigh the risks. 

Maggie Koerth: What I’m struggling with now, looking at, like, this whole big history of things, is like, where this leaves us. Part of me is looking at this and kind of having the Fauci reaction, right, of like, “I think this is a good vaccine. Just like what are they doing?”

Anna Rothschild: So, Maggie, does the U.S. need this vaccine?

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Maggie Koerth: I mean, we are contracted for enough vaccine to vaccinate everybody in the U.S. by July. So we don’t actually need AstraZeneca to get the job done here. But it is needed in a lot of other places. It’s the one that, you know, became part of, like, the international “Let’s get everybody vaccinated” effort, right? So, like, all of the contracts for how we are going to get vaccine to people in developing countries are tied to AstraZeneca

Anna Rothschild: One of the things that this has brought up for me that I do think is a positive, I guess, is the fact that, like, this Data [and] Safety Monitoring Board did exactly what it was supposed to do. And that they clearly were working in the public’s best interest to correct this mistake from AstraZeneca. And, for me at least, I find that pretty comforting, because it means that our system is working, right. Like, we have these independent boards for a reason. And they’re working to inform the public, they looped in the federal government, and it’s the process in action, which is great.

Maggie Koerth: Yeah, that has been good all the way through. I mean, like, Pfizer, Moderna did not know they had 95 percent accuracy before the independent review boards did. That should be giving us a lot of faith. That should be making us feel better. 

Anna Rothschild: Well, so this, this brings us to the big question, which is, Would you take the AstraZeneca vaccine, knowing what you do now?

Maggie Koerth: Um, I have been pretty vocal about the idea that I would absolutely take J&J. 

Anna Rothschild: Same.

Maggie Koerth: Even though the efficacy from the clinical trials is lower than Moderna and Pfizer. So this is not just a, like, “Oh, I need perfection. I need the best. I feel like I can judge what is the best.” Like, that is not what I’m saying. I personally, probably would be a little hesitant about AstraZeneca at this point.

Anna Rothschild: Me too. I’m going to need to hear from multiple independent scientists that they trust it before I go out of my way to get this one. You know, in all likelihood it’s safe and effective, but they’ve just had so many communication errors! 

Maggie Koerth: And when you have a pattern of that, I mean, like it’s effectively no different than if my kid comes down and tells me that she cleaned her room and has stuffed everything under her bed the last five times she’s said that. At a certain point, I’m not going to trust the room is clean.

Anna Rothschild: That’s a great analogy. Well, I think we should end it there. Maggie, thank you so much for chatting with me about this. It’s always a pleasure to, you know, just gab and talk about major pharmaceutical companies and …

Maggie Koerth: Girl stuff.

Anna Rothschild: Yeah, exactly!

One correction on today’s episode: For some reason, Maggie and I repeatedly said that the independent, impartial board was called the “Data Safety Monitoring Board.” It’s actually the “Data and Safety Monitoring Board.” I do not know how we got that stuck in our heads.

That’s it for this episode of PODCAST-19. If you have a question you’d like us to answer on the show, email us a voice memo at That’s ask podcast one nine at gmail dot com. I’m Anna Rothschild. Our producer is Sinduja Srinivasan. Chadwick Matlin is our executive producer. Thanks for listening. See you next time.

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Maggie Koerth was a senior reporter for FiveThirtyEight.

Anna Rothschild was FiveThirtyEight’s senior producer for video.

Sinduja Srinivasan was the producer for PODCAST-19.