The story continues
The fact that both vaccines use a viral vector and both are associated with blood clots has led many health experts to believe that the clotting problems of the two vaccines may share the same mechanism.
3. Why do women have more clots than men?
At this point, doctors still don’t know what makes women more susceptible than men, or what exposes a person to these clots. These clots can occur, although rarely, in people who do not get the vaccine. Scientists know that women are three times more likely to develop this type of clot without receiving the vaccine. Many researchers believe this is due to birth control or other hormone substitutes that women take.
4. Why can vaccines cause blood clots?
Researchers believe this specific low platelet clotting is similar to a reaction some people experience when they are given a blood thinner called heparin, called heparin-induced thrombocytopenia.
Doctors sometimes use heparin to thin a person’s blood in the event of a heart attack or blood clot when blood flow needs to be restored. But some people experience the opposite reaction and their blood ends up clotting more instead. This happens because the body triggers an unwanted immune response after receiving heparin.
In these patients, heparin binds to a product released from platelets called platelet factor 4. When this happens, the immune system views the combined platelet factor 4 and heparin as a problem, and therefore creates antibodies in response. These antibodies bind to the heparin and platelet factor 4 complex, and the body – which now thinks it needs to repair an injury – causes more clotting while using even more platelets. This results in a low platelet count observed in these patients.
When doctors looked at the blood of patients who developed clots after receiving the Johnson & Johnson or AstraZeneca vaccine, it looked a lot like the blood of people who have a low platelet heparin clotting reaction. This has led scientists and doctors to believe that the same process could lead to these clots caused by both vaccines.
This article is republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Mousumi Som, Oklahoma State University.
Mousumi Som works at the Health Sciences Center at Oklahoma State University. She received funding from Eli Lilly and NIAID for drug-related research into COVID treatments. She is affiliated with the National Board of Osteopathic Medical Examiners and the Osteopathic Founders Foundation. .