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30 Nov, 2021 13:51

Study aims to find reason for rare blood clots in people vaccinated against Covid

Study aims to find reason for rare blood clots in people vaccinated against Covid

The UK government’s Vaccine Taskforce has launched a study into the rare, but potentially deadly, cases of blood clotting and low platelet counts reported in some Covid-infected patients and people who received certain vaccines.

In a statement announcing the study on Tuesday, the University of Liverpool cited reports from March about small numbers of people seeking medical care “predominantly after the AstraZeneca vaccine.” These patients had blood clots in major veins – including those in the brain and abdomen – but also exhibited low levels of blood platelets, which are responsible for clotting.

The £1.6-million project will see scientists from across the UK research the occurrence of the adverse condition clinically known as thrombotic thrombocytopenia syndrome (TTS). It is expected to look at how common TTS was in the general population before Covid-19 and compare this against the cases identified after the pandemic began.

“The combination of blood clots with low platelet levels is very rare, and although it has been reported previously ... the clusters of cases were unusual and an association with the vaccines was suggested,” the study’s chief investigator Munir Pirmohamed said, adding that the “vast majority” of people given the vaccine do not develop TTS.

Noting that the most common side effects from Covid-19 vaccination were mild reactions lasting for two or three days, the statement said the study will examine changes in the body leading to the “unique combination of blood clots and low platelet count” seen in TTS.

In recent months, the AstraZeneca vaccine – officially known as Vaxzevria – has come under increasing scrutiny in a number of countries over the incidence of serious side effects. Both the UK’s Medicines and Healthcare products Regulatory Agency (MHRA) and the European Medicines Agency have listed the vaccine as a risk for the paralysis-causing Guillain-Barre syndrome nerve disorder after a handful of cases were reported.

Meanwhile, Denmark suspended the use of both the Vaxzevria and Janssen (Johnson & Johnson) vaccines in June after raising concerns about vaccine-induced TTS. The Danish Health Authority noted at the time that the risk-benefit “balance” was “not favourable.”

Last week, AstraZeneca CEO Pascal Soriot claimed that its Covid-19 vaccine offered longer-lasting immunity against the virus. He told the BBC that the vaccine’s roll-out to the elderly in the UK could account for the apparently lower hospitalisation rates seen in the country relative to Europe.

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