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£1.6m study to investigate blood clot risk of Covid-19 vaccines

           

Researchers to explore rare occurrences of blood clots in vaccinated people with low platelet count

A new £1.6 million study will investigate rare instances of blood clotting in major veins following vaccination from Covid-19.

The study, which is funded by the government’s Vaccine Taskforce, follows reports of a small proportion of vaccinated people being admitted to hospital with blood clots earlier this year, mainly after receiving the AstraZeneca vaccine.

As well as blood clots, patients also developed a low level of platelets, which are responsible for clotting.

Researchers from 11 institutions will work in partnership with the NHS and national agencies to study the occurrence of blood clots with low platelets—known as thrombotic thrombocytopenia syndrome (TTS)—and develop solutions.

So far, the Medicines and Healthcare products Regulatory Agency has noted 426 suspected cases of TTS and 73 deaths in the UK.

“The combination of blood clots with low platelet levels is very rare, and although it has been reported previously—including before the pandemic—the clusters of cases were unusual and an association with the vaccines was suggested,” said the study’s chief investigator, Munir Pirmohamed.

“It is important to note that the vast majority of individuals given the vaccine do not develop TTS—but between 1 in 100,000 and 1 in a million do. We do not yet understand why a vaccine that is safe for almost everyone can cause TTS in particular individuals.”

The project will investigate how common TTS was before Covid-19, as well as in those who have been vaccinated against Covid-19 and in those suffering from the virus.

Scientists will also explore why only a small number of those vaccinated against Covid-19, and also those with Covid-19 itself, develop blood-clotting disorders and investigate changes in the body that lead to the combination of blood clots and low platelet count.

“The benefit of Covid-19 vaccines still far outweighs the risks, but it’s important we understand more about the biology behind TTS and why Covid-19 vaccines can lead to it in these rare cases,” said Andy Ustianowski, a clinical lead at the National Institute for Health Research for the Covid-19 vaccination programme.

“This research is vital to help find some answers to prevent and treat TTS, and further improve the safety of current and future vaccines.”

UK Research and Innovation announced a similar study in August, saying “new research has now begun following reports of a very rare condition involving blood clots and low platelet levels after Covid-19 vaccinations”.

The UKRI study is led by the British Heart Foundation Data Science Centre—a partnership between UKRI-funded Health Data Research UK and the BHF.