Jacksonville cardiologist: Blood clots reported after J&J vaccine ‘very rare’

The type of blood clot seen after these vaccines does not happen often. News4Jax reporter Erik Avanier spoke with one of the area's leading authorities on Coronavirus vaccines.

JACKSONVILLE, Fla. – The U.S. on Tuesday recommended a pause in using the single-dose Johnson & Johnson COVID-19 vaccine to investigate rare blood clots that occurred in six women 6 to 13 days after vaccination.

Cardiologist Dr. Michael Koren, director of the Jacksonville Center for Clinical Research, has been studying this closely and said the clots, specifically called cerebral venous sinus thrombosis (CVST), so far only impact a certain demographic. All six cases were in women between the ages of 18 and 48.

“We know that cerebral venous sinus thrombosis is a condition associated with pregnancy and birth control pills, so it is possible there’s some association between this particular patient population, the vaccine,” Koren said. “So we’re looking at this rare complication, and it is possible that there may be certain groups, particularly women who have childbearing potential, that may be at high risk of this extremely rare complication.”

The clots occurred in veins that drain blood from the brain and occurred together with low platelets, the fragments in blood that normally form clots. Of the six cases, one person died, and all of the cases remain under investigation.

EXPLAINER: What’s known about COVID vaccines and rare clots

VIDEO: The U.S. recommended a pause in using the single-dose Johnson & Johnson COVID-19 vaccine to investigate rare blood clots that occurred in six women 6 to 13 days after vaccination.

Koren, who has been a cardiologist for many years and specializes in blood clots, explained CVST is an extremely rare type of clot.

“Extremely unusual. I’ve never seen this actually,” Koren said. “It’s something you read about, you’ve heard of. But I’ve treated tens of thousands of people in my career and never seen it.”

More than 6.8 million doses of the J&J vaccine have been given in the U.S., the vast majority with no or mild side effects.

“This is a very rare condition that happens 1 in a million times when you get the vaccine,” Koren said. “The benefits of the vaccines are huge, and the risks are really, really small.”

He said the likelihood of the J&J vaccine preventing death within the first two months of getting the vaccine is 1 in 2,000 -- meaning you’re 500 times more likely to have the vaccine help you prevent death than to cause this condition.

Until the pause in using the J&J vaccine ends, Koren said people should still get either the Pfizer or the Moderna vaccine because it will give them a better chance of surviving a COVID-19 infection than going unvaccinated.

“There is no question at this point that the vaccine, for most people, the vast majority of people, helps prevent death, disability, hospitalization and other complications of COVID-19,” Koren said.

The Centers for Disease Control and Prevention and the Food and Drug Administration recommend that people who were given the J&J vaccine should contact their doctor if they experience severe headache, abdominal pain, leg pain or shortness of breath within three weeks.

Meanwhile, the Jacksonville Center for Clinical Research is currently in the trial phase of the Novavax COVID-19 vaccine, and so far, there appear to be no complications associated with blood clots. If Novavax gets the all-clear from the FDA, it could become the next vaccine available.

The Associated Press contributed to this report.

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