New Delhi: British-Swedish pharma giant AstraZeneca's Covid-19 vaccine, made in collaboration with Oxford University has been found to raise the risk of vaccine-induced immune thrombocytopenia and thrombosis (VITT) -- a rare but fatal blood clotting disorder, claimed researchers on Thursday.

While not new, VITT emerged as a new disease following adenovirus vector-based Oxford-AstraZeneca vaccine -- sold as Covishield in India and Vaxzevria in Europe -- at the height of the Covid pandemic in 2021.

"An unusually dangerous blood autoantibody directed against a protein termed platelet factor 4 (or PF4)" was found as the reason for VITT.

In separate research in 2023, scientists from Canada, North America, Germany and Italy described a virtually identical disorder with the same PF4 antibody that was fatal in some cases after natural adenovirus (common cold) infection.

Now in a new research, Flinders University in Australia and other international experts found that the PF4 antibodies in both adenovirus infection-associated VITT and classic adenoviral vector VITT share identical molecular fingerprints or signatures.

"Indeed, the pathways of lethal antibody production in these disorders must be virtually identical and have similar genetic risk factors,” said Professor Tom Gordon from Flinders

The researcher noted that the "findings have the important clinical implication that lessons learned from VITT are applicable to rare cases of blood clotting after adenovirus (a common cold) infections, as well as having implications for vaccine development".

The same team had in a 2022 study "cracked the molecular code of the PF4 antibody and identified a genetic risk factor".

Their new findings, published in the New England Journal of Medicine, also have important implications for improving vaccine safety.

The research comes after AstraZeneca "accepted, in a legal document submitted to the High Court in February, that its Covid vaccine 'can, in very rare cases, cause Thrombotic Thrombocytopenic Syndrome (TTS)'."

TTS is a rare side effect that can cause people to have blood clots and a low blood platelet count. It has been linked to the death of at least 81 people in the UK as well as hundreds of serious injuries.

The company has also voluntarily withdrawn "marketing authorisation" of its Covid vaccine from Europe and other global markets.

(IANS)