Important Update about the Johnson & Johnson/Janssen COVID-19 Vaccine

Healthcare worker prepares a vaccine

Just like the Pfizer-BioNTech and Moderna vaccines, the Johnson & Johnson vaccine is given as a shot in the upper arm.

On April 13, federal and New York State health authorities recommended a temporary pause in administering the Johnson & Johnson/Janssen (J & J) vaccine while six cases of a rare blood clotting disorder are investigated, including one fatal case. Approximately seven million Americans have received this vaccine, which is given as a single dose.

As a result, MSK has suspended giving patients and staff the J & J vaccine until a further analysis is completed. 

Federal health officials stress the importance of getting vaccinated with one of the two other currently available options, Pfizer-BioNTech and Moderna, which have no safety concerns and are 90% effective in preventing COVID-19. The current pause in administering the J & J vaccine is being done out of an abundance of caution. It demonstrates how carefully any potential safety problems with vaccines are being evaluated by public health authorities.

Jodi Mones

Jodi Mones

MSK hematologist and medical oncologist Jodi Mones explains what we know at this point, pending the investigation by the Centers for Disease Control and Prevention (CDC) and the US Food and Drug Administration.

I’ve already had the J & J vaccine. What symptoms should I be watching out for?

People who have received the J & J vaccine in the last one to three weeks should monitor for these symptoms: severe headache, abdominal pain, leg pain, or shortness of breath. If you experience any of them, you should contact your primary care provider.

The signs of this blood clotting disorder are different than the more common side effects that can be seen within the first few days after the vaccine, such as a mild headaches or flu-like symptoms.

The risk to anyone vaccinated more than a month ago with the J & J vaccine is extremely low.  

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Can this blood clotting disorder be treated?

Yes. However, this clotting syndrome occurring after vaccination is not treated like a typical blood clot, so it is important if you develop symptoms of a blood clot to let your healthcare provider know whether or not you received the J & J vaccine.

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What is known about the patients who developed the clotting disorder?

According to federal health authorities, six women between the ages of 18 and 48 developed an extremely rare kind of blood clotting syndrome, characterized by very low levels of platelets and blood clots in the brain. It’s called cerebral vein sinus thrombosis with low platelets.

This rare clotting disorder is different from more common blood clots in the lungs or leg veins, affecting 300,000 to 600,000 Americans every year, according to the CDC.

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How soon after being vaccinated did the clotting occur?

The symptoms occurred between six and 13 days after vaccination.

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Are health authorities certain the clotting occurred as a result of the vaccine?

This is precisely what the investigation is trying to determine.

Cerebral vein sinus thrombosis can occur independently of a vaccine. Low platelets can also occur independently of the vaccine. It is the combination of the cerebral vein sinus thrombosis with low platelets that has caused concern and may be related to the vaccine.

It’s also possible these patients would have developed these clots without having been vaccinated.

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Have there been blood clotting problems with the Pfizer-BioNTech and Moderna vaccines?

There have been no major safety concerns or similar events reported with more than 180 million doses of these vaccines already administered. They work differently than the J & J vaccine, and MSK continues to offer them to protect against COVID-19.

It’s important to remember the risk of developing this kind of blood clot is extremely rare. It is common for health officials to pause the use of a new drug at the first indication of a potential safety concern so it can be investigated thoroughly. While it’s unsettling to read about possible serious side effects, you should be reassured by this scientific process. We will be updating information about the J & J vaccine as the situation develops.

COVID-19 Vaccine Safety and Effectiveness: Updated Information
Learn from MSK infectious disease specialist Mini Kamboj what you need to know about the COVID-19 vaccines.

April 14, 2021


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