Doctors voice concerns over bloodclots linked with vaccine

Doctors say they are homing in on the cause of blood clots that may be linked with certain coronavirus vaccines and said their findings have important implications for how to treat the condition, regardless of whether vaccines cause it. Even though the link is not firm yet, they're calling the condition vaccine-induced immune thrombotic thrombocytopenia or VITT.

It's characterized by unusual blood clotting combined with a low number of blood-clotting cells called platelets. Patients suffer from dangerous clots and, sometimes, hemorrhaging at the same time. It's been linked most firmly with the AstraZeneca coronavirus vaccine, which is in wide use in Europe and the UK.

The US Centers for Disease Control and Prevention and the Food and Drug Administration are checking to see if Johnson & Johnson's Janssen vaccine also might cause blood clots. Both AstraZeneca's vaccine and the J&J vaccine use common cold viruses called adenoviruses as a carrier and some experts suspect the body's response to those viral vectors might underlie the reaction. AstraZeneca's vaccine is not authorized in the US.