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The Johnson & Johnson Pause Shows The System Is Working

On Tuesday, the FDA announced that they were recommending a pause on administering doses of the Johnson & Johnson vaccine. On the latest episode of our coronavirus podcast, PODCAST-19, we discuss the decision, what it means for the country’s fight against COVID-19 and what it says about how the medical establishment is monitoring COVID-19 vaccines. You can find the episode and a transcript below.

Anna Rothschild: All right, guys, so we heard this news this morning. Why has the FDA recommended this pause?

A gloved hand arranging syringes of the COVID-19 vaccine on a covered table.

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Maggie Koerth: Well, so you probably remember that AstraZeneca has had some issues with a very rare and very specific clotting disorder that is not just like a normal blood clot but involves kind of a combination of symptoms that should normally, you would think, be antithetical to one another. So, having blood clots but also having a really low platelet count. And now it has turned out that this same combination of symptoms has shown up in six cases of people who have been vaccinated with Johnson & Johnson in the United States. 

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Anna Rothschild: Of those six cases, how many deaths have there been? 

Kaleigh Rogers: So there’s only been one death reported. There was also one other report of a pretty severe case, where they were in hospital — that they might still be in hospital, from what I understand.

Anna Rothschild: I know six cases is a very small number of cases. But is there any sort of rhyme or reason to exactly who is getting these rare blood clots?

Kaleigh Rogers: Yeah, so, I mean, in these six cases that we have, they were all women. And they were all between the ages of 18 and 48. So kind of skewing younger. 

Maggie Koerth: So, I think it’s important, though, to point out that six cases out of something like almost seven million doses administered is not really enough to say anything particularly definitive about who is experiencing this, what risk factors might make somebody more likely to experience this. It’s such a small number that it doesn’t necessarily tell us anything, and we could actually end up spotting patterns where the patterns mean something else. So, a good example of this is in Europe, when they’re having this side effect with AstraZeneca, is that it was kind of looking from that data like, Oh, this is something that is happening in people under 50, and in women, but then you kind of start looking a little bit closer at it. And well, they were also giving AstraZeneca primarily to people under 50. And it was also one of the first vaccines being given out to health care workers, who are primarily women. So it could have been an effect of who was getting that vaccine more than who was likely to get clots. 

Anna Rothschild: How does the background rate of this rare type of blood clotting compare to what we’ve seen with Johnson & Johnson? Like, what’s normal for the population each year?

Kaleigh Rogers: So, according to a joint CDC and FDA press conference that we had this morning, they’re not totally sure what the background rate is of this rare form of blood clotting. It’s important to note that we’re talking about what is already a really rare kind of blood clot. And it has this sort of extra twist with it that makes it even rarer. So the blood clot itself is called cerebral venous sinus thrombosis. And that occurs in about five cases per million per year. And then on top of that, they’re seeing that this blood clot is coming with thrombocytopenia, which is those low platelet rates. And that also is really rare. We don’t know exactly how many people have this kind of naturally. There’s an autoimmune form of it, and it typically affects about three to four out of every 100,000 adults and children. But with those two combined, we just don’t really have a good rate for it. Presumably, it’s quite low, because the individual rates for both of those two phenomena are quite low already. And that’s why it’s really hard to compare to blood clots that occur due to other things — that other kinds of blood clots — so you might have seen, like, some well-intentioned memes or posts on social media showing that the risk of blood clots overall, while still very low, is higher in, for example, people who take hormonal birth control, but that’s including all kinds of blood clots. So, you know, you may have heard of, like, deep vein thrombosis, for example — that’s a different kind of blood clots, including all of those in that stat. And so this is for a very specific, rare kind of blood clot. It’s combined with that other rare condition of the low platelets. And so, since we don’t have a number for that, it’s not super useful to compare those rates with the rates we’re seeing from the vaccine.

Maggie Koerth: It is interesting, though, that this is the same syndrome, the same, you know, collection of symptoms that we’ve seen with the AstraZeneca vaccine in Europe. And that had led to pauses on using that there. And researchers now think that this is probably tied together around the form that both of those vaccines are made from, which is a adenovirus that’s kind of used to carry information about the coronavirus into our cells and help our cells manufacture antibodies to protect against it. So, something about that adenovirus vector is producing this extremely rare syndrome that’s usually only seen in people who are taking a specific kind of blood thinner. 

A person wearing a medical mask holds up a vial of AstraZeneca’s COVID-19 vaccine.

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Anna Rothschild: I mean, and to be clear, I don’t think the FDA has come out and said for certain that it is related to this sort of class of vaccines, these adenovirus vaccines. That being said, they also have not seen these types of clots with the Moderna or Pfizer vaccines, which use a different delivery system called mRNA. 

Maggie Koerth: Right? Yeah, they’re really very careful sort of on how they frame this. We were listening to a press conference earlier today, and they kind of stopped short of saying that it was a, you know, vaccine-class-dependent syndrome. But they were saying that they think that it’s not a coincidence that it’s those two.

Kaleigh Rogers: Yeah, just the fact that this is such — if it was just regular blood clots, that would be one thing, but the fact that this is such a rare syndrome, that typically we don’t see that often just in a normal population, and they both came up only with these two vaccines, but not with the other two, is a flag to pay attention to. 

Maggie Koerth: And it’s a good flag — it’s a good thing that we are paying attention to it. I know, I’ve seen, like, some people sort of arguing that this shouldn’t have been, this pause shouldn’t have happened — that, you know, it, it just kind of gives the idea that it gives, like, some sort of, I don’t know, credence to anti-vaccine fears, I think is really spurious. Because this is how the system is supposed to operate. We’re supposed to pay attention to things that are dangerous and things that we can do something about like this. And we’re supposed to do something about them. And that’s what we see happening.

Kaleigh Rogers: Yeah, I mean, the fact that so, so few cases of this have come up. And the, the recommendation is still to pause, I think demonstrates how carefully they’re considering the administration of these vaccines — they’re not just throwing them out and being like, “Good luck. I hope it works,” the way a lot of anti-vaxx people might feel; this should give them more comfort, knowing that when rare things pop up, we’re still paying very close attention to it and trying to react to it immediately.

Anna Rothschild: This all, this all got found because we have multiple, you know, checks and balances on vaccines after we do these large-scale clinical trials that involve, say, 30,000 people to see what happens with the vaccine once it’s in even more people, because you can’t have a million people in a clinical trial — it would be impossible to do. So as we, you know, administer these approved vaccines to more and more people, the government keeps monitoring them to make sure that they can track any extremely rare side effects as they arise. So, it’s really sort of the process working — it’s, it’s like all of our checks and balances in action.

Kaleigh Rogers: Yeah, I think it should be comforting to people. I understand why maybe it’s not if you’re already anxious and feeling, like, unsure about how the vaccine rollout might be going.

Anna Rothschild: Right. So is there a treatment for this rare condition?

Maggie Koerth: There is. I think that that’s one of the reasons why they’re actually putting this pause on this is that this is something that’s treatable, but it’s treatable in a way that is different from how you would normally treat a blood clot situation. So, part of what this pause is doing is giving, giving a chance for, like, this information to get disseminated among health care workers so that if you show up as someone who is having a blood clot problem, and who has gotten vaccinated recently, they know to treat you in the correct way that will save your life. 

Anna Rothschild: Well, let’s talk about that. I know that there are a lot of people who just got the J&J vaccine, who’re going to be concerned that this is going to happen to them. So, what are sort of the signs and symptoms to look out for?

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Maggie Koerth: Well, I was talking to one of our readers [who] actually DM’d me earlier today with this exact question because his wife had just gotten the J&J vaccine. And I think that this is a really important point to make is that it seems like this is something that — not only is it rare, but you will — it’s not something you’re going to miss. And it’s something that is distinct from the very common side effects that go with all of these vaccines, where you kind of just feel like you have the flu, you feel just sick and high fever and yucky. It doesn’t look like that. So, what we are talking about is something that happens a median of nine days after vaccination. So it’s also not an immediate thing. And what it presents as is shortness of breath, pain in the legs, pain in the abdomen, and a headache that is so severe that we’re talking about, like, something that would make you want to go seek medical help. So that combination of things is very different from just feeling sick after getting a vaccine. It happens at a very different timing from when you just feel sick from getting the vaccine. And there’s a way to treat it. So, I think that that’s something that, I mean, to me at least, to me at least, that like alleviates some level of anxiety, because I know I’m not going to mix it up with something else or dismiss it in myself.

Anna Rothschild: Right? It’s, it’s both comforting, because you won’t mix it up with anything else. And because there is actually a way to treat this. And this pause is just giving the medical community the opportunity to sort of, like, get up to speed on, on how to deal with these cases should they arise in their hospitals. 

Kaleigh Rogers: Yeah, and I mean, it could be the case that they, they come up with some new recommendations for perhaps a subgroup of people that might be better off choosing, you know, the Pfizer, the Moderna, instead of the AstraZeneca or Johnson & Johnson — there’s going to be, like, a cost-benefit analysis that they’ll be able to put together based on that. So, I know that in the U.K. right now, for example, they’re recommending that younger patients try to get the mRNA vaccine just because their risk of severe disease is a little less, so they can maybe spend a little more time waiting to get that vaccine, whereas if you’re older, the risk of COVID is most likely going to outweigh any kind of risk of a very rare adverse side effect. 

Anna Rothschild: And I think even now, right, the FDA has recommended this pause, but if you have, you know, a primary care doctor who is somehow able to give you a vaccine, and you are at [a] really elevated risk — maybe you’re older, maybe you have preexisting conditions like diabetes — I think your medical provider is still, in consultation with you, allowed to recommend this, if there’s a really persuasive reason to administer it. 

Maggie Koerth: Yeah, I mean, that — I know that there were people, that there have been people that were, like, actively trying to get the J&J vaccine because it has a lower risk of, you know, some of these allergic reactions. And there are people with really high allergy risk for whom this is absolutely the best choice. 

Anna Rothschild: Is there sort of like a cut-off date by which, you know, after I’ve gotten this shot I’m in the clear, do you know what I mean?

Kaleigh Rogers: According to the press conference that we were listening in on today, the latest that they saw this occur in the six cases that we have so far was three weeks after the vaccine. Again, we only have six cases. So, it’s kind of hard to draw any kind of conclusions from that. But if you got the vaccine six weeks ago and have, you know, you maybe had a couple days of flu-like symptoms, and you’re feeling fine otherwise, I don’t know that I would lose any sleep over this.

Anna Rothschild: Well, thank you, guys, for speaking with me today. I have to say, I found this extremely encouraging and comforting. So I really appreciate your wisdom and knowledge. And please keep me posted on what else you discover as the story progresses.

Maggie Koerth: Thanks for having us on. 

Kaleigh Rogers: Thanks, Anna. Thanks, Maggie.

Anna Rothschild: 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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Anna Rothschild was FiveThirtyEight’s senior producer for video.

Maggie Koerth was a senior reporter for FiveThirtyEight.

Kaleigh Rogers is FiveThirtyEight’s technology and politics reporter.