Small causal link between AstraZeneca jab and blood clots, expert suspects but 'benefits outweigh risk'

30 cases of rare blood clot events out of 18.1 million doses of the AstraZeneca jabs administered have been detected. Credit: PA

ITV News Political Correspondent Hannah Miller has more


The evidence is shifting towards a very small but causal link between rare blood clots and the Oxford/AstraZeneca Covid-19 vaccine, an expert has said.

The Medicines and Healthcare products Regulatory Agency (MHRA) said it had identified 30 cases of rare blood clot events out of 18.1 million doses of the jab administered up to March 24.

There have been seven deaths among the 30 cases.

But the regulator said the benefits of the vaccine in preventing coronavirus outweigh any risks and it urged the public to continue coming forward for the jab.

The 30 cases include 22 reports of cerebral venous sinus thrombosis (CVST) and eight of other thrombosis events with low platelets.

CVST clots stop blood draining from the brain properly.

Professor Paul Hunter, a medical microbiologist at the University of East Anglia, told the BBC Radio 4 Today programme: “It is not uncommon to get clusters of rare events purely by chance.

“But once you find that cluster in one population and it then crops up in another – such as previously in the German and now in the English – then I think the chances of that being a random association is very, very low.

No blood clots have been linked to the Pfizer jab. Credit: PA

“Clearly more work needs to be done, but I think the evidence is shifting more towards it being causally related at the moment.”

However, he said the risks of taking the AstraZeneca vaccine are still far outweighed by the risks of not getting the jab.

“The chance of dying if you don’t have the vaccine is many times greater than the risk of dying from CVT (cerebral venous thrombosis) after the AstraZeneca vaccine, even if it does turn out, as I suspect it will, that this link is causal,” he said.

Germany is suspending use of the AstraZeneca vaccine for people aged under 60 due to fears of a link with rare blood clots.


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On Friday, the Dutch government also said it would temporarily halt AstraZeneca jabs for people under 60, after it received five reports of blood clots with low blood plate counts following vaccinations.

But the head of the European Medicines Agency (EMA) has said there is “no evidence” to support restricting the use of the AstraZeneca vaccine in any population.

The agency said a causal link between unusual blood clots in people who have had the vaccine is “not proven, but is possible”, also adding that the benefits of the vaccine outweigh the risks of side effects.

That view is echoed by the World Health Organisation (WHO), which has urged countries to continue using the jab.

Dr June Raine, MHRA chief executive, said: “The benefits of Covid-19 vaccine AstraZeneca in preventing Covid-19 infection and its complications continue to outweigh any risks and the public should continue to get their vaccine when invited to do so.



There were no reports of people who had the Pfizer/BioNTech suffering from blood clots.

Despite the increasing evidence of a small link between the AstraZeneca jab and blood clots, there has been no evidence of reduced takeup among the British population.

Speaking to the BBC’s Good Morning Scotland radio programme, Professor Linda Bauld of Edinburgh University said reports of blood clots were “very rare” and a direct link to the vaccine was very unlikely.

She said: “These kinds of pauses and reviews are a sign that the system is working.

“Because when you see either deaths or unlikely adverse events that you wouldn’t anticipate or you didn’t see in the trials it’s reasonable for regulators to look at this.

“The MHRA is still consistently saying there’s no cause for concern and that is absolutely the message to people.”

She added: “It doesn’t look from the behavioural response, the surveys I’ve seen, that it’s affecting uptake in the UK and that’s really important.”

Professor Bauld said she had recently received her blue letter inviting her for vaccination and she was “really looking forward” to it.


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