The latest research indicates the risks of blood clots from AstraZeneca are extremely small, with data coming out from millions of people around the world who have had the COVID-19 vaccine.
Two studies have come from the University of Edinburgh and were published in academic journal PLOS Medicine. The first by William Whiteley analysed the electronic health records of 46 million adults in England with 21 million being vaccinated from December 2020 to March 2021.
From this data, Dr Whiteley found approximately 0.9-3 people per million were likely to experience extreme side effects.
"Because of its very large size, this study has provided precise results on the risks of rare blood clotting events and of low platelet levels following COVID-19 vaccination," Dr Whiteley said.
"We showed that these risks occur only in people under 70 years old with the AstraZeneca vaccine and that the increase in risk is extremely small - no more than a few people per million vaccinated."
The second study by Steven Kerr used a data set of 11 million adults in England, Scotland and Wales, comparing the event of a rare type of blood clot in the brain in the 90 days prior to vaccination and the four weeks following the a first dose of AstraZeneca.
Findings indicated a small elevated risk of blood clotting events following vaccination with AstraZeneca, equivalent to one additional event per 4 million people vaccinated.
"[Blood clots] is an extraordinarily rare event, with an incidence of only around 3-4 per million people in a given year," Dr Kerr said.
"[It] is a serious, but extremely rare side effect of vaccination. This should be weighed against the benefits offered by vaccination, which are particularly pronounced amongst the elderly and vulnerable."
