Janssen’s COVID-19 Vaccine Pause: Insights from a Hematologist


Maria DeSancho, MD, talks personal experiences with patients, vaccine hesitancy, mRNA versus adenovirus technology, risks and types of thrombosis, and more.


Maria DeSancho, MD

Earlier this week, the US Food and Drug Administration (FDA) and US Centers for Disease Control and Prevention (CDC) announced a recommendation to pause administration of Janssen Pharmaceutical’s COVID-19 vaccine following 6 reported cases of cerebral venous thrombosis.

At the moment, there remain questions surrounding the adenovirus vaccine’s safety profile, although both agencies assured the call to halt distribution was done out of an “abundance of caution.”

HCPLive® spoke with Maria DeSancho, MD, Service Chief of the Benign Hematology Service in the Division of Hematology and Medical Oncology at NewYork-Presbyterian / Weill Cornell Medical Center, about the recent news.

DeSancho, who also works in collaboration with the American Thrombosis and Hemostasis Network (ATHN) and is principal investigator for 2 of their studies, discussed thrombosis risk and its relationship to the adenovirus vaccines.

She touched on her most recent interactions with patients, many of whom have expressed concern for their risk level, vaccination hesitancy, as well as the Moderna and Pfizer mRNA vaccines.

HCPLive: So far, we've seen 6 cases of thrombotic events related to Janssen's vaccine. All cases affected young to middle-aged women. Does that give you pause to consider other contributing factors?

DeSancho: I'm trying to compare this with what is happening in Europe with the AstraZeneca vaccine. Of the first 11 described cases, which were just published last week in The New England Journal of Medicine, 9 were women of similar age as the patients you mentioned. In general, women have a higher tendency to get autoimmune diseases. So, it seems like gender is a risk factor.

Since the FDA and CDC made their announcement, have patients reached out to you with concerns about the vaccine and their risks? If so, what has that looked like, and how have you managed it?

We've had a flood of phone calls in our practice. Some of these calls came from women who I haven't seen for, maybe, 3 years. They were panicking. I let them know that the International Society on Thrombosis and Haemostasis had already written a statement in regard to the AstraZeneca vaccine.

Since it was a similar situation, I told my patients they have to watch out for persistent severe headaches or persistent belly pain, which is another manifestation. I also told them to be aware of shortness of breath, chest pain that usually gets worse with a deep breath, or even the development of blood spots in different areas of the body. 

I made the decision to tell 2 of my patients who have an autoimmune condition to come to my office. I'm going to take a blood count just to make sure. 

I would imagine this news may further feed into certain people's hesitancy to receive a vaccine. From your unique role as a hematologist, how would you navigate this for your patients? 

I still try to encourage my patients. Not only patients, but those who work in the hospital. Believe it or not, there is significant hesitancy in administrative assistants, even though they have exposure to patients. For some of them, it's widely complex to convince them.

As a matter of fact, I had an experience yesterday with one of them telling me, "Look at what happened with Johnson & Johnson. This is more reason not to get the vaccine."

I said, "You should really see how sick people get with this virus."

We get consults for hematology on patients who are admitted with COVID because they have many hematological complications. Also, we are conducting many clinical trials for sick, critically-ill, and medically-ill COVID-19 patients with 2 different dosages of anticoagulation. So, I see these patients every day.

I think the risk of getting this complication [from the vaccine] is extremely rare. Right now, it's less than 1 in a million. The risk of getting COVID is much higher, so I think you have to balance these 2 numbers.

But, for some people, regardless of what you say, you cannot convince them. It's a dilemma. It's difficult.

In terms of levels and types of thrombotic risks, are there differences between the Moderna and Pfizer vaccines, which use mRNA technology, and the Janssen and AstraZeneca vaccines, which are both adenovirus-based? What do we know so far about the associations between the vaccine makeup, or technology used, and risk of thrombosis?

I do have to say that with the mRNA vaccines, there are some cases that we have seen—but it's difficult to ascertain whether this is what you see in the general population. Basically, we have seen some patients also with thrombotic events—for example, I do have a patient who had a pulmonary embolism, and then a DVT, approximately 4 days after he got the second dose of one of the mRNA vaccines.

I have other colleagues who have seen patients with this complication, which is different from the other type of thrombosis with low platelets seen in the other 2 vaccines [AstraZeneca and Janssen].

For the adenovirus vaccines, it seems like this type of thrombosis mimics what see in patients who receive heparin for a blood clot and get an allergic reaction resulting in low platelets. Ironically, besides having low platelets, the patients clot because the platelets are more active than usual.

I'm not sure what is in the adenovirus vaccines that can trigger this reaction, but I don't think it's just the vaccine. It is also what's going on with this specific patient and their genetic component that makes the vaccine trigger this syndrome.

In the UK, they are collecting blood from patients who have had this reaction in order to evaluate their genetic component. They are trying to fish out what could be in these patients that leads them to these severe complications.

I do think we should be more proactive in evaluating the genome of these patients in the United States.

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