Scientists link rare blood clot to AstraZeneca, J&J vax
Scientists have found a possible trigger behind the extremely rare blood clots linked to AstraZeneca and Johnson & Johnson Covid19 vaccines, an advance that may help design new and improved preventives against the viral disease.
An international team of researchers investigated vaccine-induced immune thrombotic thrombocytopenia (VITT), also known as thrombosis with thrombocytopenia syndrome (TTS), a life-threatening condition seen in a very small number of people after receiving the adenovirus vaccines.
“The mechanism which results in this condition, termed vaccine-induced immune thrombotic thrombocytopenia (VITT), was unknown,” said corresponding author of the study Abhishek Singharoy, from Arizona State University, US.
The researchers at Arizona and Cardiff University in the UK worked with AstraZeneca to analyse whether the ultra-rare side effect could be linked to the viral vector which is used in many vaccines, including those from Oxford/AstraZeneca and Johnson & Johnson.
The findings, published in the journal Science Advances, suggest it is the viral vector -- in this case, an adenovirus used to shuttle the coronavirus' genetic material into cells -- and the way it binds to platelet factor 4 (PF4) once injected that could be the potential mechanism.
In very rare cases, the scientists suggest, the viral vector may enter the bloodstream and bind to PF4, where the immune system then views this complex as foreign.
They believe this misplaced immunity could result in the release of antibodies against PF4, which bind to and activate platelets, causing them to cluster together and triggering blood clots in a very small number of people after the vaccine is administered.
Professor Alan Parker, from Cardiff University's School of Medicine, said VITT only happens in extremely rare cases because a chain of complex events needs to take place to trigger this ultra-rare side effect.
"Our data confirms PF4 can bind to adenoviruses, an important step in unravelling the mechanism underlying VITT. Establishing a mechanism could help to prevent and treat this disorder," Parker said.