UK scientists have identified markers associated with rare blood clots linked with the Oxford/AstraZeneca COVID-19 vaccine – and have issued guidance to doctors to help treat it effectively and increase survival chances. 

A team of experts, led by Dr Sue Pavord of Oxford University Hospitals (OUH) NHS Foundation Trust, issued findings that will help medical staff diagnose vaccine-induced immune thrombocytopenia (Vitt).

Thrombocytopenia is a condition where the patient has a low count of cells that help the blood clot, known as platelets. Thrombosis then occurs when blood clots block veins or arteries and can lead a stroke, heart attack, and other life-threatening conditions.

In the guidance, published in the New England Journal of Medicine, scientists said the overall mortality rate of those presenting to hospitals with definite or probable Vitt was 23% – increasing to 73% in patients with a very low platelet count.

However, Dr Pavord said it was “important to stress” that this reaction to the vaccine is “very rare”.

“In those aged under 50, incidence is around one in 50,000 people who have received the vaccine,” she said.

She also said that the team has not seen any new cases of Vitt in the last three to four weeks, suggesting that the decision to offer an alternative vaccine to under 40s may have played a role.

Dr Pavord said this had been a “tremendous relief”.

All under 40s in the UK are offered an alternative vaccine as a precaution.

Researchers evaluated 294 patients, aged between 18 and 79, 220 of whom were classed as either definite or probable cases of Vitt.

All patients had received their first dose of the Oxford jab, with symptoms appearing between five and 48 days afterwards.

Of those studied, 85% were under the age of 60, and many had no underlying medical conditions.

Treatments include a plasma exchange – where plasma is taken from the blood and replaced with new fluid – steroids to dampen the immune system, administering immunoglobulins to increase platelet count and blood thinners to prevent future clots.

Up to 28 July, the MHRA has received reports of 411 cases of major blood clots with concurrent low platelet counts in the UK following AstraZeneca vaccine.

There were 73 deaths, the MHRA said. At the time, an estimated 24.8 million first doses of the jab had been administered, and 23.6 million second doses.

Professor Michael Makris one of the study authors, said that despite the findings, the team were all “strong pro-vaccination advocates”.

Prof Makris, who himself was vaccinated using AstraZeneca, said: “I believe the whole world should be vaccinated against COVID-19.

“We are not here to say anything bad about AstraZeneca, it is a matter of targeting it.”

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