A team of scientists from Australia, Canada, and Germany has found that rare blood clots, or "vaccine-induced immune thrombocytopenia (VITT), or VITT, are caused by the immune system mistakenly attacking one of the body's proteins, platelet factor 4. The discovery was made after a study of 100 patients with VITT from around the world studied 100 patients who shared a distinctive pattern in their antibodies. The researchers found that the antibodies involved in VITT begin as antibodies that recognise an adenoviral protein called protein VII, which are likely to come from childhood infections. They also found that by changing just one small part of the antibody, it suddenly gained the ability to bind plate-factor 4 very strongly. This discovery helps explain why VITT is so rare and could potentially be modified to prevent future vaccines from forming this immune reaction.