SALT LAKE CITY (ABC4) – In very few cases, the Johnson and Johnson vaccine has caused people to develop cerebral venous sinus thrombosis, also known as CVST, according to the Centers for Disease Control and the Federal Drug Administration.

University of Utah Neurosurgeon Dr. Phil Tauskky says CVST happens when a blood clot forms in the brain, preventing blood from draining out.

“About 22% of the blood that’s being pumped by the heart goes to the brain, and when one of your main veins closes because of a clot in the brain, then the brain cannot drain the blood very well,” says Tauskky.

This can cause hemorrhaging and even strokes.

Outside of vaccine concern, Tauskky says CVST is relatively rare, noting that U of U Health sees maybe 12 cases a year. He also says that people come from all over the world for help.

“About one in a hundred thousand, and it’s more woman than men. It’s more middle-aged women,” says Tauskky. “We know that women have more venous clots than men, and then we know there’s usually some suspects that have a general predisposition for more clots.”

He said ultra-contraceptives, smoking, and even some forms of cancer can cause a person to experience CVST. Treatment is available but varies based on each situation.

Tauskky says it’s too soon to make that call on whether or not the vaccine is responsible for causing CVST.

“When you vaccinate 7 million people, some people are going to have strokes, clots, and heart attacks. At the same time, it would happen even without the vaccine. The causation is not really clear to me,” says Tauskky.

As of Monday, 6.8 million people in the U.S. had received the Johnson and Johnson vaccine without any other serious adverse reactions being reported.

“On the few numbers of cases we have seen, I’m not concerned at this point. I think it’s good to — out of an abundance of caution — look into this, but the cases have been so rare for now that I’m not concerned,” says Tauskky.

“The cases we’re hearing about from the FDA are cases where the platelet – the things that cause clotting blood — can actually clump together,” says U of U Health Dr. Richard Orlandi.

In a statement made Tuesday, the CDC and FDA said CVST was seen in combination with low levels of blood platelets.

“I think it’s important to put this in perspective that this is extremely rare complication potentially from the vaccine,” says Orlandi.

While the Johnson and Johnson news may create more vaccine hesitancy, Orlandi assures Utahns that Pfizer and Moderna are a different type of vaccine and are safe.

“The risk of the coronavirus in my mind far outweighs the risk of the vaccination with Pfizer and Moderna, but that will be an individual choice everyone has to make,” says Orlandi.

If you feel like you have a headache, blurred vision, fainting, loss of body control, or a seizure, John Hopkins University writes to get help immediately.