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J&J COVID Vaccine and Blood Clots: What This Means for People With Breast Cancer
Brian Wojciechowski, M.D.
April 13, 2021

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Brian Wojciechowski, M.D., practices medical oncology in Delaware County, Pennsylvania, at Riddle, Taylor, and Crozer hospitals and also serves as's medical adviser.

The U.S. Food and Drug Administration and the Centers for Disease Control have recommended that use of the Johnson & Johnson-Janssen COVID-19 vaccine be paused because six cases of what’s called cerebral venous sinus thrombosis with thrombocytopenia have been diagnosed after people received the vaccine. Basically, a blot clot was found in the veins that drain blood from the brain, and the people also had very low levels of platelets, a type of cell that helps the blood to clot.

Listen to the episode to hear Dr. Wojciechowski explain:

  • what these rare clots are and how they happen
  • what people who’ve received the J&J vaccine should know
  • how he’s advising his patients with breast cancer

Running time: 22:08

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Show Full Transcript

Jamie DePolo: Hello, thanks for listening. Our guest is Brian Wojciechowski, M.D., who practices medical oncology in Delaware County, Pennsylvania, at Riddle, Taylor, and Crozer hospitals, and also serves as’s medical adviser. A native of south Philadelphia, he trained at Temple University School of Medicine and Lankenau Medical Center. Dr. Wojciechowski is a sought-after speaker on the topics of medical ethics and the biology of cancer.

The U.S. Food and Drug Administration and the Centers for Disease Control have recommended that use of the Johnson & Johnson COVID-19 vaccine be paused because six cases of what's called cerebral venous sinus thrombosis with thrombocytopenia have been diagnosed after people received the vaccine. Basically, this means a blood clot was found in the veins that drain blood from the brain, and the people also had very low levels of platelets, which is a type of cell that helps the blood to clot.

Dr. Wojciechowski joins us to explain what these rare clots are, how they happen, and what it means for people being treated for breast cancer. Dr. Wojo, welcome back to the Podcast, always good to talk to you.

Dr. Brian Wojciechowski: Thank you, Jamie, it’s good to talk to you again.

Jamie DePolo: So, first, can you help us understand and explain exactly what a cerebral venous sinus thrombosis is, and exactly how rare are these clots?

Dr. Brian Wojciechowski: Sure, Jamie. The cerebral venous sinuses are, basically, the veins that drain blood from the brain. So, arteries take blood to an organ, and veins take blood away from the organ back to the heart. These are pretty uncommon, and probably affect about 5 in a million people per year.

Jamie DePolo: Okay. Even before the vaccine, they were still extremely rare?

Dr. Brian Wojciechowski: That’s correct, and the problem with these types of clots is that they can cause strokes.

Jamie DePolo: Okay. Okay, because, obviously, the blood then gets backed up in the brain, and that’s a problem?

Dr. Brian Wojciechowski: The blood gets backed up in the brain and fresh blood can’t get in, and sometimes the pressure that builds up behind the blockage can actually cause the blood vessels to break, and you get brain hemorrhage or bleeding into the brain. So these are very serious and can be life threatening.

Jamie DePolo: Okay. Okay, and now, what is thrombocytopenia?

Dr. Brian Wojciechowski: Thrombocytopenia is a fancy medical term that means low platelets. Your platelets are the tiny cells in your blood that normally function to prevent bleeding. So typically, if your platelets are low, you're at risk of bleeding, and if your platelets are too high, typically and classically, you're at risk for clots.

Jamie DePolo: Okay. So, help me understand this because this is what's been puzzling me. If thrombocytopenia, as you said, it’s very low levels of platelets, and the platelets are what helps the blood to clot, how can somebody who has very low platelets get blood clots? What's the vaccine doing here, why is this happening, do we know?

Dr. Brian Wojciechowski: Yeah, Jamie, it’s paradoxical because normally we think of low platelets causing bleeding. In this particular type of low platelets, though, the risk is actually for the blood to clot, and the reason is because there is an autoimmune reaction against the platelets that causes them to clump in blood vessels, and the platelets get incorporated into these clots, so you actually get low platelets. Paradoxically, you get blood clots because the inner lining of the blood vessel is damaged by this autoimmune process, and all the platelets get sort of sucked into the clot.

Jamie DePolo: Okay. Okay, thank you, I was struggling to understand what was going on. So, it seems then the vaccine is provoking this autoimmune reaction, that then leads to the blood clots. So is this condition, I know it’s rare, but is it more concerning for people who have an underlying immune system disorder or who actually have thrombocytopenia? Because I know my brother has the genetic version, and so I’m just wondering, is this reaction caused by the vaccine, is that more concerning for any particular groups of people?

Dr. Brian Wojciechowski: Yeah, that’s a great question, and one overlying theme here is that we don’t know a lot of these answers with any degree of certainty. So this condition actually is technically a new disease — they’ve named it VITT — and a lot of what we’re going to be talking about and a lot of what's going around is speculation. We really don’t know if someone has an autoimmune disease or if someone has low platelets normally, if it’s going to be worse for that person or not.

Jamie DePolo: Okay, so that still needs to be studied. Do we know anything about people who are on blood thinners already? Because my understanding is that’s really the concern that the FDA had, that’s why they put the pause on the vaccines because they wanted to get the word out to people in the healthcare industry that, “Hey, if you see somebody with this happening, don’t automatically give them a blood thinner because that can make it worse.” So I’m wondering, if somebody is on heparin or on warfarin already, again, is this more of a concern for them, do we know that?

Dr. Brian Wojciechowski: One thing we do know for certain is that heparin and this condition do not mix. So this condition, VITT — it stands for vaccine-induced thrombotic thrombocytopenia — is very similar to another condition called HIT, which is heparin-induced thrombocytopenia. Everything about this condition mimics heparin-induced thrombocytopenia including the low platelets and the risk of blood clot, except people with VITT were not exposed to heparin, in most cases, and heparin can make the condition worse.

So yeah, one of the main reasons why they're doing this pause — and there’s a number of different reasons, but one of the main reasons — was that they want to get the word out that if you see this condition as a doctor, your initial reflex may be to treat it with heparin because that’s a blood thinner, and that’s generally the first blood thinner we think of when we’re treating a patient with blood clots. But in this case, heparin can make it worse, and it’s a big no-no.

Now, other blood thinners, like warfarin, Xarelto [chemical name: rivaroxaban], or Eliquis [chemical name: apixaban] are not problematic, so it really depends on the blood thinner that you're on.

Jamie DePolo: I see. Okay. So, the concern is really with the heparin and not the other ones?

Dr. Brian Wojciechowski: Correct.

Jamie DePolo: Okay. Okay, good to know. Now, I know that the AstraZeneca COVID vaccine — and that’s not approved in the U.S., it’s not even authorized for emergency use in the U.S. — has also been linked to these rare blood clots, to this condition, and the Pfizer and the Moderna vaccines have not. And I know the FDA was hesitant to say that it’s linked to these vaccines — with the J&J and the AstraZeneca, they use the viral vector, they use an adenovirus like the common cold. Do we know any more about what's going on there? My understanding is that if somebody’s had a Pfizer or Moderna vaccine, they don’t really need to worry about this condition?

Dr. Brian Wojciechowski: So, the first thing I’ll say is that the Pfizer and the Moderna vaccines are mRNA vaccines, and the AstraZeneca and the J&J vaccines are adenoviral vector vaccines. So they actually put DNA into the nucleus of the immune cells, so it’s DNA versus mRNA vaccines. And that’s the main difference, and it’s interesting that it’s only the adenovirus vaccines, the AstraZeneca and the J&J, that seem to be associated with this blood-clotting condition. There’s been no similar safety concern with the mRNA vaccines, which are Pfizer and Moderna.

Jamie DePolo: Okay, so we don’t really know why the adenovirus vaccines seem to be linked to it and the mRNA vaccines don’t? We don’t really know why that is yet, or do we?

Dr. Brian Wojciechowski: No, we don’t know why that is. The investigations are ongoing, there’s a lot of speculation, could it have something to do with DNA versus mRNA. But that would be just speculating at this point, which I want to try to avoid.

Jamie DePolo: Sure. Sure, I understand. Now, the six people in the U.S. who have been diagnosed with this rare condition, the VITT, they were all women between the ages of 18 and 48. Do we have any idea why women seem to be more affected?

Dr. Brian Wojciechowski: No, unfortunately, we have no idea at this point.

Jamie DePolo: Now, I guess what I first thought of, too, is what about people who are being treated with, say, tamoxifen or other medicines that are linked to a higher risk of blood clots. Is this more concerning for them, do we have any ideas about that?

Dr. Brian Wojciechowski: Again, it’s too early to know if women on tamoxifen are at any higher risk of clots related to the vaccine than women who are not. I will say this, that the mechanism of blood clotting with tamoxifen is completely different than the mechanism of blood clotting with the vaccine. And it seems that getting a clot from the vaccine is a very rare event, and the risk of getting the clot with tamoxifen is much higher than the risk of getting a clot with the vaccine.

Also, with the vaccines, you get clots in these strange places. It’s not just the cerebral venous sinus, it’s also in the portal veins, the splanchnic veins — so that’s the veins in the stomach that drain the spleen and the bowel and the liver. So it’s different types of blood clots, different mechanism of action, and different rates. So I suspect — and I’m only speculating here — but I suspect that women on tamoxifen probably shouldn't worry about this too much.

Jamie DePolo: Okay. And I did read there’s six cases of this condition out of, I think it’s 6.8 million doses of the J&J vaccine given, so that’s less than a 1 in a million chance. Which is very rare, obviously. And my understanding is that while the FDA put this pause on it, the feeling still is that the benefits of being vaccinated outweigh this risk. Is that correct?

Dr. Brian Wojciechowski: I think that’s still an open question, to tell you the truth, because they’ve paused the vaccine. So they're really not sure if the benefits outweigh the risks, at this point, especially considering the fact that there’s other vaccines available.

And we don’t know the true rate of this condition with the vaccine. So you can’t really say that there’s been six cases reported and there’s been 7 million vaccines, so divide the number of cases by the number of vaccines and you have the rate. You can’t really say that’s the rate, because those are just six cases that have been reported, and there may be other cases that have not been reported or were not recognized as this condition, so the rate could be significantly higher.

What I know about conditions like this, like what I mentioned about heparin, is that that condition is very rare. It’s fairly uncommon in people who get heparin, but it’s still about 1 or 2% of people that get heparin, which is a lot higher than the rate we’re potentially looking at with the vaccine. So I don’t want to go ahead and say it is extremely rare, I think we need to look at it more, I think the FDA needs to investigate any other cases that may have come up. But it should be fairly uncommon.

Jamie DePolo: Okay. Okay. Thank you for helping me understand that. And since we’re talking about that, we should probably quickly go over the symptoms. My understanding is, it’s severe headache, severe abdominal pain, pain in the legs, and I think there’s one other and I can’t remember. But what should people do? I know that flu-like symptoms after the vaccine are common, but I guess, in this case, we’re talking very severe headache, very severe abdominal pain, very severe leg pain — should people just go straight to the ER if that happens, should they call their doctor?

Dr. Brian Wojciechowski: I think if there’s any concern, it’s not wrong to go to the ER, and it’s certainly not wrong to call the doctor. A lot of the symptoms after the vaccine are nonspecific: you can get headache, you can get fevers, you can get leg pain, you can get abdominal pain. And all of those symptoms can be symptoms associated with blood clots, as well. But I think in the case of having a blood clot, you're right, Jamie, that you're looking for symptoms of greater severity. So additionally, if, for example, you have sudden pain, redness, or swelling in one leg and not the other, that would be much more likely to come from a blood clot than a vaccine reaction.

Jamie DePolo: Oh, okay.

Dr. Brian Wojciechowski: If you have the sudden onset of the worst headache of your life, that would be much more likely to be coming from a clot in the veins in your brain than just a normal, run-of-the-mill vaccine reaction. And again, severe abdominal pain, as you said. So yeah, it really is the severity, but I would tell people just call your doctor, that’s what we’re here for, to help figure out what's what and tease out what's really going on.

Jamie DePolo: Okay, and I guess the important thing, too, would be to tell your doctor which vaccine you had and when you had it?

Dr. Brian Wojciechowski: That’s right, and I forgot to mention the sudden onset of chest pain or shortness of breath would be very concerning for a blood clot, and you really shouldn't see that as a vaccine reaction.

Jamie DePolo: Okay. Okay. And I guess the other thing I had read was that the people that we know of so far, the six cases, all happened I think approximately 9 days after the dose of vaccine. So what experts seem to be saying is that if you got the vaccine, say, 2 weeks ago and you're fine, you probably don’t have to worry. Is that correct? In other words, is there this small window when these blood clots could form?

Dr. Brian Wojciechowski: So, I’m going to go with 3 weeks.

Jamie DePolo: Okay.

Dr. Brian Wojciechowski: Yeah, in the studies from Europe that I looked at, the longest period of time after the vaccine where someone had a clot was 16 days, so I’m going to say 2 to 3 weeks. After that, you're good to go in terms of what we know right now. Now, that could change as the FDA investigates these cases further, but as far as we know right now, it’s unlikely after 3 weeks.

Jamie DePolo: Okay. Also, good to know. So, how are you advising the people you treat for breast cancer, does it make sense for them to get the Pfizer or the Moderna vaccine instead, if they have an option?

Dr. Brian Wojciechowski: I do feel comfortable advising my cancer patients to get the vaccines, especially the Pfizer and the Moderna, because now there’s been 180 million doses of those vaccines given, and there’s been no similar safety concerns. I do think that probably they would’ve come up by now with so many doses given.

Now, our patients really don’t even have the option, right now, to have the adenoviral vaccines, the J&J and and the AstraZeneca, because AstraZeneca was never approved in the U.S., and the J&J is on pause. So as of right now, Pfizer and Moderna are the only options, and we have been encouraging our patients to get the vaccine if they can, even patients on chemotherapy or radiation for breast cancer.

Jamie DePolo: Okay. Okay, good. Now, is there anything else, say somebody who’s currently being treated for cancer and they got the J&J vaccine, say, maybe only a week ago, how are you advising them, what should they know?

Dr. Brian Wojciechowski: I think the thing to do right now is just be vigilant, and if one of my patients asked me about it, I would say, “Hey, look for sudden onset of shortness of breath, chest pain, severe headache, swelling in the leg, especially one leg and not the other, and unexplained abdominal pain.”

Jamie DePolo: Okay, so really people have to know their bodies and be, as you said, be vigilant about these particular symptoms?

Dr. Brian Wojciechowski: That’s right. And I don’t want to see people lose sleep over it right now, because, again, we don’t know the exact rate or the incidence of these blood clots with the J&J vaccine right now, but it should be fairly uncommon. It should be fairly uncommon, and again, that’s a matter of speculation, and we’ll know more in the next several weeks, but it does not seem to be a common side effect.

Jamie DePolo: Okay. And I know the FDA said this is a pause, not a complete halt, but we don’t really know how long it’s going to be before there’s enough data to decide whether the J&J vaccine can be used again, do we?

Dr. Brian Wojciechowski: No, we don’t yet, and the CDC and the FDA are investigating that right now, so hopefully we’ll know something within the next week or 2.

Jamie DePolo: Okay. Okay. Dr. Wojciechowski, thank you so much, this has been so helpful, I really appreciate your insights on this.

Dr. Brian Wojciechowski: Thanks for having me, Jamie, it was fun, as usual.

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