Video report by ITV News Europe Editor James Mates
The bloc has become frustrated after AstraZeneca warned it would not be able to deliver as many vaccines in the first quarter to the EU as it originally promised.
This is on top of Pfizer saying last week it was having to temporarily cut supply to the EU in order to increase production at one of its factories.
The EU has got off to a slow start in the race to vaccinate its population, with its best-performing country (Denmark) only vaccinating 3.6 people per 100 of its population compared to the UK's 10.4.
What has the EU said?
The EU has faced criticism for its slow rollout and in response, the European Commission threatened to impose controls on vaccines that are produced in their countries.
European health commissioner Stella Kyriakides accused pharmaceutical company AstraZeneca, which worked with Oxford University on the vaccine’s development, of failing to give a valid explanation for failing to deliver doses to the bloc.
Ms Kyriakides warned the EU “will take any action required to protect its citizens and rights”, she said in a broadcast address that an “export transparency mechanism” will be installed “as soon as possible”.
“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,” she said.
Will this affect the supply of vaccines to the UK?
Of the three vaccines approved in the UK, any potential restrictions on exports from the EU would only affect the Pfizer-BioNTech jab.
The UK's supply of the Oxford-AstraZeneca vaccine is not believed to be impacted as our consignment for the jab is made mostly in Oxfordshire and Staffordshire.
The UK has not yet received any of the Moderna jab - the third vaccine approved by regulators - and does not expect to get any until spring.
Boris Johnson has said he has “total confidence” in the UK’s supply of vaccines.
The Prime Minister told a Downing Street press briefing that the delivery of vaccines was a “multinational effort” and the UK would continue to work with European partners.
What has the government said?
The Government said it was in “close contact” with suppliers after the European Commission issued the warning amid a row with AstraZeneca over a shortfall of doses for member states.
Government vaccine tsar Nadhim Zahawi said he was “confident” that the Pfizer and AstraZeneca supply would not be disrupted.
Nadhim Zahawi "confident" supply will not be disrupted
Mr Zahawi told ITV News he was "confident that we have line of sight of the volumes coming through" and added he expected "millions of doses" in the coming weeks.
He said pointed the UK's success so far as his reason for his confidence, with 6.5 million people already vaccinated and almost 500,000 doses given on Saturday.
A spokeswoman for the government said: “We remain in close contact with all of our vaccine suppliers.
“Our vaccine supply and scheduled deliveries will fully support offering the first dose to all four priority groups by February 15.”
Boris Johnson told a briefing: “All I would say is obviously we expect and hope that our EU friends will honour all contracts and we will continue … we fully expect that will happen … and we continue to work with friends and partners in the EU, and indeed around the world, because the delivery of the vaccine has been a multinational effort, and the delivery of the vaccine is multinational as well, because the virus knows no borders.”
What are the problems the EU is facing?
The EU has not yet approved the AstraZeneca vaccine but has ordered 300 million doses of the jab.
It is expected it will be given the green light by the end of the month.
Last week AstraZeneca announced its yields had produced less than expected and warned this would impact the EU's supply.
The company has not confirmed how much the lower production will impact supply but Reuters reported that deliveries would be cut by 60% in the first quarter.
The EU has already suffered setbacks to its supply of vaccines as Pfizer cut temporarily lowered production at one of its sites in Belgium to increase output.
The EU has ordered 600 million doses of the Pfizer-BioNTech vaccine and it is the only one currently approved to be used in the bloc.
Head of the European Commission Ursula Von De Leyen has pledged to vaccinate 70% of the EU's adults by end of August.