A team of researchers at McMaster University in Hamilton found the cause of rare but sometimes fatal blood clots caused by certain vaccines. The blood clotting reaction is known as vaccine-induced immune thrombotic thrombocytopenia (VITT). According to researchers, it’s much more severe than a typical blood clot because veins that drain blood from the brain are obstructed and can potentially cause fatal bleeding. It’s believed that the findings will put scientists on the path of finding a way to better diagnose and treat VITT, possibly prevent it, and potentially make vaccines safer. "Our work also answers important questions about the connection between antibodies and clotting," said Ishac Nazy, principal investigator and corresponding author of the study.