Some 30 cases of blood clots had been reported to the European Medicines Agency (EMA) by March 10, among almost five million people vaccinated.
The Medicines and Healthcare products Regulatory Agency (MHRA) said that in the UK leading up until February 28, it had received 30 reports of blood clots in people who had the Oxford/AstraZeneca jab.
While investigations are ongoing, several countries have suspended the use of the AstraZeneca vaccine, including France, Germany, Italy and Denmark.
However, the MHRA and World Health Organization have said the benefits of the vaccine far outweigh the risks of side effects and AstraZeneca vaccine rollout continues in the UK.
The World Health Organization (WHO) said in a statement: “For the moment, based on the evidence reviewed to date by the EMA, the benefits of the AstraZeneca vaccine in preventing hospitalisation and death due to Covid-19 outweigh the risks of side effects.”
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Several experts have highlighted on Twitter how blood clots are a natural occurrence in the general population and the cases reported in vaccine recipients are not necessarily linked to the vaccine.
Referring to the EMA’s report of 30 “thromboembolic events”, David Spiegelhalter said in an article for the Guardian: “We can try a quick back-of-the-envelope calculation.
“Deep vein thromboses (DVTs) happen to around one person per 1,000 each year, and probably more in the older population being vaccinated.
Sir Michael Marmot of the UCL Institute Health Equity tweeted in response to David Spiegelhalter’s article on the topic: “Interesting. there are fewer DVTs among recipients of the vaccine than you would expect by chance.”
Former GP Charles West also replied on Twitter: “It would be more logical to suggest that the Oxford AstraZeneca vaccine prevents blood clots.
“Has there been deliberate rumour-mongering here?”
The MHRA said more than 11 million doses of AstraZeneca had been given in the UK so far.
A statement said: “Such reports are not proven side effects of the vaccine. Blood clots can occur naturally and are not uncommon.”
Blood clots have been reported as a symptom in people who have Covid-19 and experts have suggested there is a greater risk of blood clots developing in people infected with Covid than those who are vaccinated against the virus.
Professor Anthony Harnden, deputy chairman of the Joint Committee on Vaccination and Immunisation (JCVI), said “the risk of developing blood clots from Covid far, far exceeds any potential risk from the vaccination.”