Science Alert COVID vaccines saved millions of lives, but months into the rollout, a small number of people began developing dangerous blood clots in unusual parts of the body.
These only happened after vaccines that used a modified adenovirus to deliver their payload, such as the AstraZeneca vaccine. Why these blood clots formed was a mystery – until now.
The condition was named vaccine-induced immune thrombocytopenia and thrombosis, or VITT. It happens when the immune system mistakenly attacks one of the body’s own proteins, called platelet factor 4.
Antibodies that recognise platelet factor 4 are actually part of normal immune responses, but in VITT, the antibodies that develop are unusually sticky. They cling to platelet factor 4, pulling together many molecules and forming large clusters of proteins called “immune complexes”, leading to dangerous blood clots.
Over the last few years, we have been working on the biology of VITT, primarily focusing on how these antibodies activate platelets. However, the way that vaccination triggers these antibodies to form was one of the main mysteries in this disease.