The four countries have signed an agreement with the group, formed in 1999 from the merger of the Swedish company Astra and British company Zeneca, which provides for the supply of a vaccine to all EU member states as soon it is discovered, said the German Ministry of Health.

AstraZeneca is partnering in the enterprise with Britain's Oxford University, which has pioneered the inoculation.

The firm has been building separate supply chains around the world during the tests, striking other deals earlier this month to double production capacity to more than two billion doses.

“This agreement will ensure that hundreds of millions of Europeans have access to Oxford University's vaccine following approval,” Chief Executive Pascal Soriot said in a statement.

“With our European supply chain due to begin production soon, we hope to make the vaccine available widely and rapidly.”

Oxford University began initial trials with hundreds of volunteers in April and is now expanding them to 10,000 participants.

The development of a vaccine could be successfully completed by the end of the year, German government sources told AFP.

The doses announced Saturday, potentially rising to 400 million, “must be distributed to all member states that want to participate, depending on the size of their population,” the German ministry said.

“In order for the vaccines to be available in large numbers very quickly after their possible approval this year or next year, production capacities must be guaranteed by contract now.”

According to the World Bank, the EU has a population of around 447 million.

German Minister of Health Jens Spahn said that “the swift and coordinated action of a group of member states” would see “all EU citizens” stand to benefit.

The European Commission defended the idea on Friday that EU countries should join up to guarantee privileged access to a future vaccine, arguing strongly for the establishment of advance purchase contracts.

With the laboratories trying to find a vaccine in record time — 12 to 18 months instead of several years in normal times – these advance payments allow them to invest in production, even though the clinical trials on humans have not yet been finalised.

This commitment would give member states the right to buy doses at a certain price once the vaccine is available, in return for the risk taken in terms of investments.

Major pharmaceutical groups are engaged in a race to develop a vaccine against the coronavirus, which has so far killed more than 417,000 people and infected more than 7.4 million worldwide.