A BREAKTHROUGH study lead by scientists in Oxford has revealed 'devastating' findings on blood clotting in some adults after by Covid-19 vaccination.

This follows the emergence earlier this year of vaccine-induced immune thrombotic thrombocytopenia (VITT), which can lead to abnormal blood clot formation, swelling and bleeding in the brain.

VITT is characterised by a blockage of the veins and a marked reduction of platelets – tiny cells in the blood that form clots to stop or prevent bleeding.

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The paper, published in the New England Journal of Medicine, looks at symptoms, signs and outcomes of the first 220 cases of patients with the syndrome in the UK.

The research team, led by Dr Sue Pavord of Oxford University Hospitals (OUH) NHS Foundation Trust, found that the overall mortality rate of patients with VITT was 23 per cent.

The study showed that the chances of death increase significantly the lower the platelet count and the greater the activation of the blood clotting system, increasing to 73 per cent in patients with a very low platelet count and intracranial haemorrhage following blood clots in the brain.

Banbury Cake: A generic stock photo to illustrate a blood clot in the body. Credit: Alamy/PA. must only be used to accompany PA Feature HEALTH Blood Clots.A generic stock photo to illustrate a blood clot in the body. Credit: Alamy/PA. must only be used to accompany PA Feature HEALTH Blood Clots.

Dr Pavord, a consultant haematologist at OUH, said: "It is important to stress that this kind of reaction to the Oxford-AstraZeneca vaccine is very rare.

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"In those aged under 50, incidence is around one in 50,000 people who have received the vaccine.

"But our study shows that for those who develop VITT, it can be devastating.

"It often affects young, otherwise healthy vaccine recipients and has high mortality.

"It is particularly dangerous when the patient has a low platelet count and bleeding in the brain.

"VITT is a very new syndrome, and we are still working out what the most effective treatment is, but identifying prognostic markers has helped to determine what is the more effective way to manage the condition."

Dr Pavord confirmed that treatments for patients with the most severe disease now include plasma exchange, which has shown some success.

Some 85 per cent of the patients studied were under the age of 60, despite most of the elderly population having been vaccinated.

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Almost all of those presenting to hospital experienced the condition between five and 30 days after their first vaccination with the Oxford AstraZeneca vaccine.

The study also showed there was no difference in incidence between the sexes, and no prior medical condition was seen more often than expected for the general population.

Dr Pavord added: "We have worked relentlessly to understand and manage this new condition, so that the hugely successful vaccine rollout can continue, which is the most viable solution to the global pandemic."