Loading ...A blood clot is what it sounds like—a gel-like clump of blood. Small blood clots form whenever you cut or scrape your skin to plug up the injured area and stop the bleeding. But they are dangerous when they form within a blood vessel, where they can cause thrombosis (meaning they block blood flow), a condition that kills up to 100,000 people a year in the United States. “Those clots typically occur in people who are bedridden or hospitalized, or have other medical issues related to inflammation or infection or cancer,” says Yale Medicine hematologist Robert Bona, MD. They are also more likely to occur in women who are pregnant or on oral contraceptives, or in people who have hereditary disorders that predispose them to blood clotting.
As mentioned above, the clotting condition associated with the J&J vaccine is called thrombosis with thrombocytopenia (TTS). Thrombosis occurs when blood clots block veins or arteries, and thrombocytopenia is a condition characterized by abnormally low platelet levels in the blood. The latter is unusual in someone with a major blood clot because platelets are colorless blood cells that have the function of helping blood clot.
“The mechanism of the action of these clots has been quite unusual and, frankly, that has surprised me,” says Dr. Bona. “There are definitely a lot of questions.”