BRUSSELS: The EU is holding talks with Moderna on buying more COVID-19 vaccine and AstraZeneca, with which talks have stalled, has suggested delivering doses of its own vaccine made outside Europe to make up for supply cuts, two EU sources said.

The European Union has set a target of vaccinating 70% of its adult population by the end of the summer, but has struggled to secure the doses promised by pharmaceutical companies.

It is now trying to expand its reserve of vaccines, which already amount to nearly 2.3 billion doses from six drugmakers for its population of about 450 million.

The EU is negotiating a new supply deal with Moderna that could nearly double the volume of vaccine doses from the US biotech firm, two senior EU officials involved in the talks told Reuters.

They asked for anonymity as the talks are confidential.

Under the deal being negotiated, the EU would secure 150 million additional doses from Moderna, on top of 160 million that have already been booked and have started being rolled out last month.

One of the two officials said some of the doses under the new deal could be delivered by June.

The second was more cautious, pointing to difficulties Moderna has faced delivering just 10 million doses to the EU in the first quarter of 2021.

The volume of shots available could, however, be boosted if the number of doses that can be extracted from each Moderna vial is increased.

Moderna declined comment on the talks with the EU. But it said it was holding discussions with regulatory authorities in different countries on the possibility of increasing the number of doses in vials to 15 from 10.

The Commission did not immediately respond to a request for comment.

The EU is also close to finalising talks with Novavax for 200 million doses, one of the officials said, confirming a Reuters report from last week.

"BUILT ON SAND"

On Friday, officials in Brussels and executives from AstraZeneca discussed the cut in deliveries announced by the Anglo-Swedish drugmaker last month, when it told the EU it had reduced its supply targets for the bloc because of a production problem.

That would have cut deliveries to 31 million doses through March instead of the at least 80 million initially agreed.

Under pressure, AstraZeneca, which developed its vaccine with Oxford University, later offered to lift supplies to 40 million for the first quarter.

The EU and AstraZeneca are now holding weekly meetings to find ways to boost production quickly, the two sources said.

AstraZeneca executives told EU officials on Friday that to accelerate supplies to the bloc, it could provide it with some doses manufactured outside Europe, the two sources said. One said the Serum Institute of India (SII) could be a supplier.

The British drugs regulator is also auditing manufacturing processes at the SII plant, a move that could pave the way for AstraZeneca's vaccine to be shipped from there to Britain and other countries, two sources said.

SII is the main provider of vaccines to poorer countries under a scheme co-led by the World Health Organization. It is unclear whether these supplies could be affected by possible deliveries to wealthier countries.

AstraZeneca also mentioned a US manufacturing facility as a possible supplier for the EU, but did not indicate volumes or timing of deliveries, one of the sources said.

AstraZeneca and the SII were not immediately available to comment.

Both EU sources said the company's new offers lacked clarity. One source said it was still not clear whether AstraZeneca could deliver the 40 million doses pledged for the first three months of 2021, and there were only vague commitments for the second quarter.

"It's all built on sand," the official said.

EU officials have said the US vaccine factory AstraZeneca has mentioned is in Baltimore, but have given no more details.

Under deals announced last year, Catalent's Maryland facility will make the drug substance used in AstraZeneca's vaccine and Emergent BioSolutions Inc is making the shot at its Baltimore facility.

Deliveries from factories outside the EU would need to be authorised by the EU drug regulator, EU officials said.

The EU has said two factories producing AstraZeneca's vaccine in Britain should supply the EU under its contract with the company. AstraZeneca has said the British government prevented exports of the vaccine citing its own supply contract.

The British government has declined to say whether its contract with AstraZeneca gives priority to British supplies.