The astonishing move could scupper the arrival of tens of millions of doses of the life-saving jab in Britain.
Shocked MPs branded the EU “mean-spirited and selfish” for making such a brazen threat.
And around 25million doses that have not yet been dispatched to Britain could be threatened by an export ban, The Sun understands.
AstraZeneca, which makes the Oxford vaccine, also has factories in the EU.
But it is believed the majority of the vaccine used on Britons is made at its plants in Oxford and Keele, Staffordshire.
Risking a major diplomatic row, EU health boss Stella Kyriakides said they will take “any action required” to help their crisis-hit vaccination programme.
She warned: “We want clarity on transactions and full transparency concerning the export of vaccines from the EU.
“In the future, all companies producing vaccines against Covid-19 in the EU will have to provide early notification whenever they want to export vaccines to third countries.
“Humanitarian deliveries are of course not affected by this.
“The European Union will take any action required to protect its citizens and rights.”
Also piling in, the German Health Minister Jens Spahn added: “We, as the EU, must be able to know whether and what vaccines are being exported from the EU.
“Only that way can we understand whether our EU contracts with the producers are being served fairly.
“An obligation to get approval for vaccine exports on the EU level makes sense.”
The EU is angry after AstraZeneca cut the number of vaccines it is sending to the bloc, but did not slash British supplies.
The UK has jabbed five times as many people per head of the population as the EU.
British MPs savaged the EU for resorting to such desperate threats during a pandemic.
“The UK has quite legitimately opened up access to its vaccines and made it very clear it intends vaccines to be sent all around the world.
“Contrast that with the mean-spirited, selfish behaviour of the EU. They ought to be ashamed of themselves.”
Tory MP Peter Bone said: “The United Kingdom has provided an extraordinary number of vaccines — we have led the world in it.
“We have vaccinated more people in the last three days than France has.
“I am shocked if the European superstate is trying to block the export of vaccine just because of its inefficiency and bureaucracy.
“It is just another example of why we should be out of this terrible organisation.
“It is outrageous from the EU. I think most people will find that quite shocking.”
Last night German officials said in highly inflammatory anonymous claims published in the country’s newspaper Bild that AstraZeneca’s vaccine was just 8% effective for those over 65.
However AstraZeneca and the Oxford team that developed the jab quickly rubbished the claims calling them “completely incorrect”.
A spokesperson for AstraZeneca, said: “Reports that the AstraZeneca/Oxford vaccine efficacy is as low as 8% in adults over 65 years are completely incorrect.
“In the UK, the JCVI supported use in this population and MHRA included this group without dose adjustment in the authorisation for emergency supply.
“In November, we published data in The Lancet demonstrating that older adults showed strong immune responses to the vaccine, with 100% of older adults generating spike-specific antibodies after the second dose.”
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An Oxford spokesperson said: “There is no basis for the claims of low efficacy of the Oxford-AstraZeneca vaccine which have been circulating in the media.
“The results of the clinical trials have already been published transparently in 5 peer-reviewed scientific publications showing similar immune responses in younger and older adults and a good safety profile, and high efficacy in younger adults.
“Furthermore, the preliminary efficacy data in older adults are consistent with that observed in younger adults.”
Sage scientist Professor John Edmunds says people shouldn’t be ‘overly concerned’ about single Covid dose reports
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