What you need to know about risk of rare blood clots
A rare and severe type of blood clot has been detected in six people after they received the Johnson & Johnson COVID-19 vaccine, according to the the Centers for Disease Control and Prevention and U.S. Food and Drug Administration.
The CDC reports that the six cases all presented with cerebral venous sinus thrombosis (CVST), in combination with low blood platelet levels (thrombocytopenia). The clots were detected among women between the ages of 18 and 48, and symptoms started 6 to 13 days after the one-shot vaccine.
Dr. George Williams, associate professor of anesthesiology and critical care medicine at McGovern Medical School at UTHealth, said CVST is a brain-based blood clot with symptoms similar to a stroke. The clot affects the brain’s ability to drain blood, which creates a backlog of pressure that can lead to brain swelling and a possible brain hemorrhage.
“It’s a blood clot occurring in the brain, but it’s not a stroke,” Williams said. “It’s really on the other end where the blood is trying to leave the brain, but the exits are blocked.”
CVST symptoms include a recurring headache, blurry vision, loss of consciousness, inability to control movement in part of the body, seizures or a coma. Williams said a CVSTrelated headache is one that doesn’t go away and occurs simultaneously with other symptoms — weakness or seizures.
Williams says that anyone experiencing these symptoms should call their doctor.
CVST is treatable once detected in a person’s brain, Williams said, and patients typically respond well to treatment.
CVST cases have been increasing in recent decades. “There is some discussion that it might be related to the use of oral contraceptives, but there’s not a definitive conclusion on that,” Williams said. “There is more risk of CVST in females than males in general.”
Early Tuesday, the CDC and FDA recommended that vaccine providers pause their administration of the Johnson & Johnson COVID-19 vaccine. The Houston Health Department heeded the recommendation and will stop administering Johnson & Johnson until further guidance is provided. The Texas Department of State Health Services asked state vaccine providers to halt the vaccine’s administration, as well.
CVST is extremely rare, the agency reported, but it recommends a moratorium “out of an abundance of caution.”
“More than 6 million Johnson & Johnson vaccine doses have been administered, and we’re talking less than 10 cases of CVST have been reported,” Williams said. “That rate is not what happens in the general population as a whole, but the government is being very cautious and attentive to this, as they should be.”