A UK study has said that COVID-19 patients face a higher risk of developing blood clots than those vaccinated with AstraZeneca or Pfizer shots. Initial reports of vaccines causing blood clots had led to hesitancy among  people leading to a slow rate of vaccination.

“For every 10 million people who receive the first dose of AstraZeneca, about 66 more will suffer from a blood-clotting syndrome than during normal circumstances,” according to the study published in the British Medical Journal, reports Bloomberg. 

The study followed 29 million people who received their first doses of either AstraZeneca or Pfizer vaccine between December, 2020 and April and also tracked about 1.7 million COVID-19 patients, the report added.

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This study comes as a boost for vaccines dogged by safety concerns. Many developed countries had stopped the use of the said vaccines among older adults because of concerns about an elevated risk of blood clots.

The study also said that it could not be definitively said that the clots were caused by the vaccines, though regulators have identified a possible link. 

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Earlier, a research team led by Dr Sue Pavord of the Oxford University Hospitals NHS Foundation Trust, had said that blood clots that can be caused by the Oxford/AstraZeneca coronavirus vaccine can be deadly but are very rare.

Their paper, published in the ‘New England Journal of Medicine’, looked at symptoms, signs and outcomes of the first 220 UK cases of VITT and found that the overall mortality rate of those presenting to hospitals with definite or probable VITT was just over 22 per cent.

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The chances of death increased 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 (cerebral venous sinus thrombosis – CVST).