Scientists at Cardiff University believe they may have found the “trigger” behind extremely rare blood clot complications stemming from the Oxford/AstraZeneca coronavirus vaccine.
Estimates suggest the vaccine is thought to have saved about a million lives from coronavirus.
However, despite having played a major part in the UK's vaccination programme, concerns about rare blood clots associated with the AstraZeneca meant people under the age of 40 in the UK and overseas are no longer offered it.
These clots, known as vaccine-induced immune thrombotic thrombocytopenia, have been linked to 73 deaths out of nearly 50 million doses of AstraZeneca given in the UK.
Scientists have regularly reaffirmed that contracting coronavirus is far more likely to cause clots than having the vaccine, however, concerns started a hunt to figure out what was causing the extremely rare side effect.
A team in Cardiff was given emergency government funding to find the answers.
That team, alongside researchers in the United States, have detailed how a protein in the blood is attracted to a key part of the vaccine.
Researchers think this may spark a chain reaction in the immune system that can culminate in the development of blood clots – a condition known as vaccine-induced immune thrombotic thrombocytopenia (VITT).
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.
“We hope our findings can be used to better understand the rare side effects of these new vaccines – and potentially to design new and improved vaccines to turn the tide on this global pandemic."
Scientists from AstraZeneca also took part in the research.
A spokeswoman for the company said: “Although the research is not definitive, it offers interesting insights and AstraZeneca is exploring ways to leverage these findings as part of our efforts to remove this extremely rare side effect.”
The company said the vaccine is thought to have saved more than a million lives and prevented 50 million cases of Covid globally.