This month, we welcome Dr. Stephan Moll to answer frequently asked questions on COVID-19 vaccination. Dr. Moll is a Professor of Medicine at the University of North Carolina in the Department of Medicine and the Division of Hematology-Oncology. His clinical interest is coagulation, with a focus on thrombosis (blood clots) and anticoagulation. He takes a special interest in the clinical-medical education of patients, the public, and healthcare professionals, and is a cofounder of the UNC Blood Clot Education Program Clot Connectwww.clotcotconnect.org.
In this webinar, he will…
  • Explain the situation around the Johnson & Johnson (J&J) vaccine and rare blood clots.*
  • Address questions on COVID-19 vaccination in the context of genetic clotting disorders, autoimmune diseases, and anticoagulation (blood thinners)

A full transcript of the Q&A can be found under the video.

*Please note that this video was recorded when use of the J&J vaccine was paused in the U.S. after six cases of rare blood clots with low platelets—called thrombosis thrombocytopenia syndrome (TTS)—were reported in women who received the vaccine. As of April 21, 15 additional cases of TTS have been identified in women who’ve received the J&J vaccine.

As of April 23, 2021, the CDC and FDA have given the green light to resume the use of the J&J COVID-19 vaccine in U.S. adults. The vaccine label will include a warning about the increased (but rare) risk for blood clots and low platelets.

Key Takeaways:

  • The Moderna and Pfizer vaccines that are currently available in the U.S. do not increase the risk for blood clots
  • The J&J vaccine has been associated with very rare, unusual clots.
  • Patients who have received the J&J vaccine within the last 2-4 weeks should seek medical attention if they develop unusual symptoms, such as:
    • A significant headache (the worst headache ever)
    • Neurological symptoms (like weakness on one side or the other, or speech problems)
    • Unusual abdominal symptoms, such as severe stomach pain, nausea, or vomiting that’s out of the blue
    • Other signs of blood clots, including leg pain, chest pain, or difficulty breathing
  • Patients with a history of blood clots, patients with autoimmune disease, and patients who take a blood thinner are not at higher risk for developing a blood clot if they get the Moderna or Pfizer vaccine.

*This video and transcription were recorded when the use of the J&J vaccine was paused in the U.S. The CDC and FDA have re-authorized use of the vaccine as of April 23, 2021.*

Hello, I’m Stephan Moll. I am a hematologist, clinical researcher, and educator at the University of North Carolina in Chapel Hill, North Carolina. I’m here today to answer pressing questions that you may have about COVID-19 vaccination, particularly in regard to risk for thrombosis. 

Q: The use of the Johnson & Johnson (J&J) vaccine has been paused in the U.S. after six reported cases of rare blood clots. What should patients know about the J&J vaccine and blood clot risk?

These are rare blood clots and should not sway people away from getting the vaccinations that we have in the U.S. currently (the Moderna or the Pfizer vaccine). I’m going to reference these rare blood clots in a minute, but I do want to get the main message out first: the two vaccines we have available, Moderna and Pfizer, are not known to increase risks for blood clots, including clots like deep vein thrombosis (DVT) and pulmonary embolism (PE), (i.e., blood clots in the legs or in the lung), or the other rare blood clots that have been observed with the vaccine in Europe or with the Johnson & Johnson vaccine. (We’ll get back to J&J.) 

With the currently available vaccines, even people who have had a blood clot or people who are on blood thinners are not at increased risk for blood clots with these vaccines. So, there’s no concern, and people should get the vaccine and not hold off for any reason. That’s the key message, I think. 

Regarding the J&J vaccine, which is also called the Janssen vaccine, there is a medically relevant story there. It’s not that clinically relevant for the general public because the vaccine has been paused in the U.S. and is not available at the moment. But the observation has been, in the last few weeks in Europe (with the AstraZeneca vaccine, which is not available in the U.S), that there have been a number of unusual clots. Those are clots around the brain called cerebral and sinus vein thrombosis (CVST) and some unusual clots in the abdomen – or “unusual” is not the right word, but rather rareclots in the abdomen called splanchnic vein thrombosis or portal or splenic vein thrombosis, or mesenteric vein thrombosis.

Now, there have been a number of cases in Europe, but overall, it’s still a relatively rare occurrence. The unusual thing about these clots has been that not only are they in unusual locations, but that they are also associated with a decrease in blood platelets. It’s an immune phenomenon that has been described and more clearly identified now, where the immune system in certain patients makes antibodies that activate platelets and leads to a lowering of the platelets, but the activation of platelets also leads to blood clots. 

Now the interesting thing—and the initially upsetting and alerting news—was that, in the U.S. last week, there were six patients who developed a similar picture. All six had CVST and all six had low platelets. (And this was with the J&J vaccine, or the Janssen vaccine. This issue has not been observed with the Moderna or Pfizer vaccines.) But these six case reports led to a temporary halting of the J&J vaccine until it becomes clear how commonly this issue occurs, who’s at risk for it, and how we should deal with the situation. 

These complications are of some concern for the patients who have had the J&J vaccine in the last few weeks because the observation has been, in Europe, as well as with these six cases, that these blood clots happen within two weeks of having received the vaccine, so within 14 days. Now, if somebody has had the J&J vaccine more than two weeks ago or more than, let’s just even say for safety, more than 4 weeks ago, it’s not expected that the J&J vaccine would cause any problems in those people. But if people have received the vaccine within the last, let’s say 4 weeks, or more accurately in the last 2 weeks, then there is some risk for these unusual clots – but the risk is very, very small, given the millions of people that have been vaccinated. 

Q: What are the symptoms of CVST and what should people watch out for? 

The typical symptom of CVST, a clot around the brain, is a headache, and there can be symptoms with the headache such as neurological symptoms, vision disturbances, vision loss, neurological symptoms similar to a stroke, weakness on one side or the other, or language difficulties where one cannot speak or has garbled speech. Those would be symptoms that are noteworthy to the patient and the family. And it’s not just a mild or moderate headache – it would be something that’s unusual, maybe the worst headache ever. But if people are concerned, they certainly should talk to their physician and be evaluated for it. 

Q: And what are the symptoms of other rare clots, like the clots in the abdomen? 

Those symptoms are, most likely, something like pronounced nausea, pronounced unusual vomiting, or maybe diarrhea that’s really out of the ordinary. The patient would typically know that this is just not “how I typically feel.” Certainly, they should reach out to their physician and be evaluated. 

Now, it may well be that some people develop more usual clots, such as DVT, the blood clot in the leg, or a PE, a clot in the lung – but that’s not clear and has not been well studied neither in Europe nor here. Does it occur? Is that really how this disorder, this J&J or AstraZeneca-associated disorder happens? Certainly, if a new clot develops in the legs or in the lung within 4 weeks of the J&J vaccine, it’s worthwhile asking, “was this maybe due to the J&J vaccine?” 

And if somebody presents with such a DVT and PE, the first step for the emergency room physician or general practitioner is to ask about the vaccine: “have you received this in the last 4 weeks?” The second step is to obtain what’s called a CBC, or a complete blood count, to assess if there are lowered platelets, because this disorder is presenting as low platelets plus a blood clot. If it’s only a blood clot with normal platelets, that’s not the disorder associated with the vaccine. 

Q: If I have a history of blood clots or a genetic clotting disorder*, is it safe to get a COVID-19 vaccine? 

*Genetic clotting disorders include factor V Leiden, protein S or C deficiency, or a prothrombin gene mutation, though this is not a complete list.

It is safe to get one of the two vaccines that we have in the U.S., currently Moderna or Pfizer. There’s no increased risk in anybody, including those who have a history of DVT or PE, or who are on anticoagulation. There is no increased risk for blood clots. Now, having said that, there may be some confusion or concern in people because we know that COVID-19 infection has been associated with blood clots, particularly among people who are in the hospital or intensive care unit. That was a significant concern, particularly last year when COVID-19 first came about. In the hospital, we routinely give blood thinners to prevent blood clots, but again, that’s within the context of COVID-19 infection. The COVID-19 vaccineis not associated with blood clots. 

Q: If I have an autoimmune disorder* and a history of blood clots, is it safe to get a COVID-19 vaccine?

*Autoimmune disorders include lupus, antiphospholipid syndrome (APLS), idiopathic thrombocytopenic purpura (ITP), rheumatoid arthritis, psoriasis, and inflammatory bowel disease, though this is not a complete list.

Well, that’s a good question. In general, yes. However, the vaccine does activate the immune system – that’s what the vaccine is meant to do; you produce antibodies against the virus. A few months ago, you may remember there was a case in Florida where a physician, a gynecologist, developed what’s called immune thrombocytopenic purpura (ITP), which is due to the immune system making antibodies that attack platelets—that lower the platelets—then leading to bleeding. So, activation of the immune system seems to occur in a few people. So yes, we do think about that, and particularly, as a hematologist, I think about it when I follow patients who have established ITP because that happens even outside of the immunizations. 

When those patients get the immunization, we do have a little bit of an increased concern or need to observe whether they develop a worsening of their thrombocytopenia or reactivation of the ITP. A similar thought process would, I would expect, occur with a rheumatologist who follows somebody with lupus or rheumatoid arthritis, or a gastroenterologist who follows somebody with ulcerative colitis or Crohn’s disease, etc. Often, those patients are on certain medications and their disease is under control. But certainly, those individuals should talk to their rheumatologist or respective gastroenterologist, and in the case of ITP, to the hematologist. What we’ve done in some ITP patients is we get blood counts, a CBC, every so often after the immunization—such as 5 days later, 10 days later, and then maybe again another 5 days later—because the immune response would be expected to occur in the first week to two weeks. 

So, if there’s a drop in platelets or maybe a reactivation of an immune process, you would expect that would happen relatively soon after the vaccine. But in general, people with immune disorders should strongly think about getting the vaccine, and that’s what the rheumatologists here at UNC tell their patients, and the societies have come up with statements, too. These patients should consider getting the vaccine because the risk for developing COVID-19 and complications from COVID-19, including dying or long-term issues from COVID-19 infection, are significantly higher than the low risk (or potentially even rare risk) of developing a reactivation of the immune disorder. 

Q: If I take an anticoagulant (blood thinner), is it safe to get a COVID-19 vaccine?

Whatever anticoagulant or blood thinner you are on, it’s appropriate for you to get the vaccine. You get the flu vaccine once per year, and most people don’t change their blood thinner dosing. However, in the patient on warfarin (or Jantoven®, which is the brand name for warfarin), the INR, the level of thinness, may fluctuate in people. So, it’s worthwhile to get an INR maybe 5-7 days before you get the shot to make sure your blood is not very, very thin at the time of the shot. The shot is given into the muscle of the deltoid, the big shoulder muscle. So, if your blood is very thin, due to a very high INR, you may want to hold the warfarin for a few days and let the INR come down to the 2 to 3 range, or maybe even a 2 to 4 range, and then get the shot. 

With the other blood thinners—rivaroxaban (Xarelto®), apixaban (Eliquis®), dabigatran (Pradaxa®), or edoxaban (Savaysa®), the oral drugs that you don’t need to routinely monitor—you can get the shot even when you’re on the blood thinner because your blood is not overly thinned. But I’ve also told patients look, if you take the drug typically in the morning, then it’s easy enough not to take it that morning because we know occasionally a patient even not on blood thinners may develop a hematoma, a big bruise in the arm. It’s not common, but it does occur, and that risk is likely a little bit higher if you’re on a blood thinner. So, I think it’s very reasonable in the morning not to take the dose of the direct oral anticoagulant (DOAC) and then get the shot and take it afterwards. 

However, people are on blood thinners for different reasons, and I don’t know what blood thinner you’re on, so you should talk to your primary care physician or whoever follows your blood thinner before making any changes. 

Q: Is there anything else I should know about COVID-19 vaccination if I’m on a blood thinner?

So typically, a very small needle is used to administer these vaccines called a gauge 25. A slightly larger needle is called a gauge 23 or 22. (So the numbers go down, yet the size is bigger – it’s a little confusing.) The optimal needle size is gauge 25, and that’s what I would like if I was on a blood thinner. But a 23 or 22 is very likely also sufficient, though if the injection center, the vaccination center, has a small needle, that would be preferred. If you, as a patient, tell them, “I’m on a blood thinner, can I have a gauge 25 needle?”, that would be the optimal approach. I would not say, “if you don’t have a 25, I’m not going to take the vaccination.” That would be wrong. You’re better off getting the vaccination. 

Q: If I take aspirin or another antiplatelet medication (such as Plavix®), can I get a COVID-19 vaccine?

Yes. There should not be any concern or any modification of the treatment plan. You should just get the vaccine. 

Q:  What are the key takeaways regarding COVID-19 vaccination and blood clots?

The key information is, number 1, the two vaccines we have available in the U.S. at this point, the Moderna and Pfizer vaccines, do not increase the risk for blood clots. There’s no signal, so people should get the vaccine. 

Secondly, the vaccine that was just halted this week, the J&J or Janssen vaccine, has been associated with very rare, unusual clots, and that’s why its use has been halted.

Thirdly, the people who have had the J&J vaccine within the last two or four weeks—and let’s say four weeks—who develop unusual symptoms such as significant headache (the worst headache ever), neurological symptoms like weakness on one side or the other, speech problems, or who develop unusual abdominal symptoms, such as severe stomach pain, nausea, or vomiting that’s out of the blue, should think, “could I have a blood clot around the brain or in the abdomen that may be associated with the J&J vaccine?”, and they should seek medical attention. 

Fourthly, people who have a history of blood clots, either DVT or PE or other blood clots—or who are on a blood thinner—are not at higher risk for developing a recurrence of the blood clot, a new blood clot, if they get one of the two vaccines that we have available. 

And lastly, in general, everybody should think, yes, I should get a vaccine. There are very few patients who should not get it, and those are typically the ones who have an allergy to one of the components of the vaccine. But the blood clot issue with the two vaccines we have available in the U.S. (Moderna and Pfizer) should not have any influence on someone getting vaccinated at this time.