Researchers have connected the Covid-19 vaccine created by AstraZeneca and Oxford University to an increased risk of vaccine-induced immune thrombocytopenia and thrombosis (VITT), a rare and possibly lethal blood clotting condition.

Though not a novel illness, VITT became recognized as a separate illness after the Covishield in India and Vaxzevria in Europe adenovirus vector-based Oxford-AstraZeneca vaccine was used during the Covid-19 pandemic in 2021.

VITT was shown to be caused by an "unusually dangerous blood autoantibody" against platelet factor 4 (PF4).

According to a 2023 study, following spontaneous viral infections, researchers from Canada, North America, Germany, and Italy described a similar condition involving the same PF4 antibody that was occasionally fatal.

Along with other researchers, Flinders University in Australia recently discovered that the molecular signatures of PF4 antibodies in conventional adenoviral vector VITT and VITT linked to adenovirus infections are the same.

Flinders University professor Tom Gordon clarified that these diseases probably share genetic risk factors and follow the same processes for creating deadly antibodies. The results imply that vaccine development may be aided by awareness of uncommon blood clotting events following viral infections derived from VITT cases.

The same research group had previously found a genetic risk factor and the molecular code of the PF4 antibody in a 2022 study. Their recent results, which were published in the New England Journal of Medicine, have great potential to improve vaccine safety.

In a February judicial filing to the High Court, AstraZeneca admitted that its Covid-19 vaccination can, in extremely rare circumstances, result in thrombotic thrombocytopenic syndrome (TTS). Rare side effect TTS has been associated with low platelet counts and blood clots, which in the UK have caused at least 81 deaths and many serious injuries. AstraZeneca has therefore willingly removed its Covid-19 vaccination from European and other international markets.