Medical Examiner

The J&J Vaccine Pause Is Science Working Like It’s Supposed To

A syringe and vials labeled "COVID-19 Coronavirus Vaccine Injection Only" in front of the Johnson & Johnson logo
Reuters/Dado Ruvic

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On Tuesday, the Food and Drug Administration and the Centers for Disease Control and Prevention announced a “temporary pause” in distribution of the Johnson & Johnson COVID-19 vaccine, after six people who received the shot were diagnosed with a rare blood clot in their brains. To make sense of the news, I called up Tara Haelle, a science journalist and the author of Vaccination Investigation: The History and Science of Vaccines. We talked on Thursday’s episode of What Next about how worried people should be, why the J&J vaccine is being compared to hormonal birth control, and whether the messaging surrounding the pause will affect vaccine hesitancy. Our conversation has been condensed and edited for clarity.

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Mary Harris: I wonder if you were sort of expecting this day would come.

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Tara Haelle: Yes, I was, and I wasn’t the only one. We’re giving out a vaccine to what’s ultimately going to end up being, like, 300 million people in the United States alone. The odds of something not happening are smaller than the odds of something happening. You could have all the time in the world and you could never produce a product that’s not going to have an adverse reaction in some people.

Let’s talk about exactly why the U.S. government is pausing distribution of the Johnson & Johnson vaccine. It’s because of a rare condition called cerebral venous sinus thrombosis. Can you tell me what that is?

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CVST is actually two different things together. It’s CVST, and it’s a condition called thrombocytopenia, which means a drop in platelets level. And it is probably connected.

What’s weird is that one is a clotting disorder and the other is a bleeding disorder, and it seems like you shouldn’t get both at the same time.

Yes. CVST is a blood clot in the brain, basically. And thrombocytopenia is a drop in the platelets. The platelets are the blood cells that encourage clotting. So how does this happen, where at the same time you have less clotting and you have a blood clot? This particular condition, what they think this is, is the same thing that’s happening with the AstraZeneca vaccine. And in order for it to make sense, we have to go and look at this other condition called heparin-induced thrombocytopenia. Heparin is a blood thinner—typically it’s what you see in the liquid that’s in the hospital when people have IVs on most of the time.

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And it’s usually what you would give if someone has a blood clot.

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Yep. In some people who receive heparin, the heparin causes your body to make autoantibodies—antibodies against your own body. They grab on to this one thing called the platelet factor 4, or PF4. PF4 is a piece of a platelet. They make these antibodies against that piece of the platelet, so in addition to going after heparin, they go after platelets, and they simultaneously destroy some platelets and activate the others.

Is what’s happening here exactly the same as what’s happening with the AstraZeneca vaccine or slightly different somehow?

That’s what we need to find out. There are several reasons for doing the pause. One is just to investigate it. What’s going on? Is this what’s happening with the AstraZeneca vaccine? Does that mean this is how we should treat it? The reason I think it’s probably going to end up being the same thing is they’re making the same recommendation not to treat it with heparin—and that’s the exact same thing they’re saying with the AstraZeneca vaccine.

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And that’s why it was so important for the FDA and CDC to get out there, because if you’re a doctor, you might think, I know how to treat this, you just give this drug. But that may be the opposite of what you want to do.

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Exactly.

Is it fair to say there’s a one in a million chance of developing this condition?

So far, yes. It’s one in 1.1 million, if you want to be pedantic. But we still need to find out if there are other cases that we aren’t aware of. That’s yet another reason for the pause: Find out if there’s anyone else who’s experiencing this. Make sure that people know what the symptoms are so they can monitor themselves, because this is diagnosable and it is treatable if you know what symptoms you’re looking for. And so it’s good that everybody is paying attention to the fact that this has been paused, because it’s going to lead them to say, “What do I have to watch for?” And that’s what they need to happen. They need people on the watch.

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People have tried to contextualize what we know about the risk of the J&J shot. Many have pointed out that birth control pills and COVID itself also come with a risk of clots—a much higher risk, actually. And while those clots might not be in your brain, they’re definitely still dangerous. Do you think those comparisons are valid?

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It’s really hard for humans to do risk evaluation. We suck at it, frankly. We’re just not very good at assessing risk. It’s why we’re afraid of flying, but not of driving most of the time.

Like you said, hormonal birth control that contains estrogen, [the blood clot risk is] about one out of a thousand, sometimes one out of 500. And I was in that group. I developed a serious blood clot, and it was misdiagnosed. I was 18. This was way back in the ’90s. They didn’t realize how common it could be—it’s still rare, but one in a thousand is more common than one in a million, which is what they thought it was back then. So that’s yet another reason for pausing: Make sure that this is the actual frequency that they think it is.

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At the same time, pregnancy, which is what you’re trying to prevent with birth control pills, the risk of clots is one in 300. That’s three times more frequent. And one of the big defining features of COVID has been blood clots. The risk of it once you’re hospitalized actually leaps considerably. If you’re in ICU, it’s one in five people have blood clots.

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We don’t know much about the people who’ve developed clots from the vaccine—just that they are, for the most part, women. And you think that might be important.

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That was absolutely the first thing I thought of. A lot of people have noticed that and thought, wait, were they on birth control pills?

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Because it already boosts your risk of clots?

Exactly. It’s a reasonable question. They were of reproductive age. They were in the 18-to-48 age range. However, women in general have a higher risk of blood clots. And for this particular condition, the “normal” condition, not necessarily related to vaccines, the women get it three times more than men. And the reason is that we have estrogen, and estrogen encourages clotting anyway. It’s also why we have a higher risk of clots during pregnancy.

So it makes sense biologically.

Exactly.

A lot of people are like, “Why didn’t they catch this in the trials?” Well, this is a one in a million event. You don’t have a million people in a clinical trial. You’re just not going to find a one in a million thing unless you’re testing millions of people.

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I feel like that’s a hard thing for people like Dr. Anthony Fauci to say out loud, because there is so much hesitancy and worry already that this is getting out there too quickly. Do you think they should have messaged it better, or is there just no good way to say that out loud?

I don’t know if there is a good way to say that out loud. Public health messaging has always been incredibly difficult, and we’ve been getting better at it, but we certainly have a long way to go. And part of the challenge is it’s two-pronged. One is that people don’t necessarily understand how science is an iterative process. It’s not a body of knowledge. It’s an ongoing, stumbling-toward-the-light process of identifying knowledge, which means that when things change, it doesn’t mean that facts change, it means new stuff has come to light. I was thinking of The Dude in The Big Lebowski: “New shit has come to light.” That’s the history of science right there.

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And that also happens in public health. But layered on top of that is our complete inability to assess risks rationally. So I think no matter how they messaged it, it was going to be difficult to convey it, because people don’t think about the fact that we face risks every day of our lives, no matter what we do. Every single thing we do has a risk.

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Do you think this is going to affect vaccine hesitancy globally, even beyond this particular shot?

I don’t know if it will beyond this particular shot, any more than any other thing has, but I definitely think it’s going to play a role in how people make decisions. We already are seeing that with the AstraZeneca vaccine. It hasn’t been authorized in the United States, but it’s been authorized in many other countries, and they are seeing some hesitancy around that. But that’s also a result of poor messaging. There hasn’t been good information coming from different governments and from AstraZeneca itself as to what’s going on. I think they’re doing a much better job with messaging with the Johnson & Johnson vaccine. But there are still going to be people who say, “Whoa, blood clot, that’s scary. I don’t think I want to get that vaccine.”

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If people do start shunning this vaccine for whatever reason, is there enough of the other vaccines out there to get the U.S. to herd immunity?

Maybe not right away, but assuming nothing happens to the manufacturing facilities, there will eventually, and I know that they’re ramping up production. So I think there’s going to be some people, but I don’t think it necessarily will be as big an impact as we think. I think there will still be people who want to get whatever shot they can, and if Johnson & Johnson’s offered to them, that’s the shot they’ll take. I mean, if I were offered the Johnson & Johnson shot right now for my kids and I didn’t have the option of choosing a shot, I would still take that risk. To me a one in a million chance is not something that I’m going to worry about. In a way, I’ve already taken that chance with them by having them get certain other vaccines that might have caused an anaphylactic reaction.

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My concern is that the Johnson & Johnson vaccine becomes the vaccine of last resort, the vaccine that’s going to people in prisons, people who are unhoused, people who don’t have choices. I could see that happening so easily.

I can, too. We’ve already seen huge inequities in how these vaccines are rolled out, so I’m not going to paint any kind of rosy picture. One thing I will say is if a particular community wants a particular vaccine as a community, I think they should have access to that vaccine, especially if they’re an oppressed community that has not often had a lot of choice in what kind of health care options they receive.

If someone has had a Johnson & Johnson vaccine in the last week or two, what should they be doing right now to make sure they’re OK? If they start to feel some kind of way, who do they call?

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First, they should pay attention to their body and the symptoms. The symptoms to watch out for are a really severe headache that just won’t go away, shortness of breath, blurred vision or any kind of neurological effects like that, any kind of pain in the abdomen or the chest, swelling or redness or paleness or coldness in the arms or legs, a seizure, anything like that. Any of these things might happen in the 21 days after getting the vaccine, because if this is in fact the vaccine-induced thrombocytopenia, then the thing that’s causing it is the antibodies, and it takes up to three weeks for your body to make those antibodies. So these symptoms could start anywhere from a week to 2½ weeks after you get the vaccine. If you have these symptoms, you should contact your primary care provider if you have one. If you don’t have one or if your primary care provider refers you out, then you may need to go to an urgent care clinic or to an emergency department.

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