In April 2021, U.S. federal health regulators recommended a pause in J&J distribution while they investigated reports of the rare side effect impacting women ages 18 to 48.

The cause was the possibility of blood clots developing – a condition called thrombosis with thrombocytopenia syndrome (TTS) – with the one-shot Johnson & Johnson (Janssen) vaccine.

A subsequent review of available data showed that J&J vaccine’s known and potential benefits outweighed its known and potential risks. However, the Centers for Disease Control and Prevention and Food and Drug Administration did advise women younger than 50 to be aware of the risk, noting that it had not been seen in the Pfizer and Moderna vaccines.

Still, the numbers are small. The likelihood of developing TTS after J&J's COVID vaccine is four cases per 1 million doses, the CDC said. And, keep in mind, tens of millions of doses have been safely administered in the U.S.

Also important, one study determined that people were eight to 10 times more likely to develop blood clots in the brain from having COVID itself rather than from receiving either of the Pfizer or Moderna vaccines.

Dr. Asif Wahid
Dr. Asif Wahid

In line with the CDC’s recommendation to use mRNA vaccines over J&J, Novant Health is offering Moderna and Pfizer COVID immunizations for the primary series. People who experienced an allergic reaction to an mRNA vaccine can, however, opt to receive a J&J booster at Novant Health. Individuals who prefer or are only eligible for the J&J vaccine are also encouraged to check NCDHHS or a retail pharmacy for availability.

In the meantime, Dr. Asif Wahid, a cardiologist at Novant Health Cardiology in Thomasville and Lexington, answered some of the most pressing questions.

Let’s start from the top: What is a blood clot?

Blood clots are blood-formed blockages in the vein that can affect circulation. Depending on the type and severity, they can be mild and require little treatment, or they can lead to serious injury or even death. Deep vein thrombosis (DVT) is one of the most common types of blood clots, and it typically develops in the patient’s leg or arm. If left untreated, the clot can break free and travel to the lungs.

Blood clots in general are fairly common and affect an estimated 900,000 Americans each year. Anyone can be affected by a blood clot. Risk factors increase if patients are hospitalized, pregnant or have cancer. A long drive or long flight can also put you at risk for blood clots.

Can COVID-19 cause blood clots?

Yes. Research is currently underway to investigate how COVID can affect the blood. Some COVID patients have developed blood clots in multiple places throughout the body, and patients that have diabetes or high blood pressure are at a higher risk.

We believe this clotting is caused by increased levels of inflammation in the body. As a result, patients are at a higher risk for heart attack, stroke and organ damage.

In children, this condition is called multisystem inflammatory syndrome (MIS-C), and can damage the heart to such an extent that some children will need lifelong monitoring.

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What kind of blood clot has been associated with the J&J vaccine?

TTS is a rare condition in which blood clots are accompanied by a low level of platelets, the colorless blood cells that help blood to clot. When working properly, platelets stop bleeding after injuries. However, if platelets drop below normal levels, patients are at increased risk of cerebral venous sinus thrombosis (CVST), a blood clot in the brain that can be life-threatening.

Patients that have developed the rare TTS after receiving the Johnson & Johnson vaccine typically develop symptoms within two weeks. Symptoms may include severe headache, trouble speaking or breathing and swelling. Similar occurrences of TTS were observed following the rollout of the AstraZeneca COVID-19 vaccine in Europe. AstraZeneca has not been approved in the United States.

If patients notice any of these symptoms, they should seek help right away. While blood clots are normally treated with a blood thinner medication, patients that develop TTS as a result of the vaccine may require a different treatment regimen.

When speaking to patients, I like to remind them that the latest CDC recommendation should give us all increased confidence in the overall safety and efficacy process. Before coming to market, each vaccine had to go through a strict approval process, and the CDC and FDA continue to monitor for possible side effects.

Bottom line: Ultimately, the data showed that the likelihood of developing TTS from the Johnson & Johnson vaccine was very rare. And the benefits outweighed the risks.