A row has erupted between the European Union, the United Kingdom and pharmaceutical company AstraZeneca over the supply of coronavirus vaccines.

The EU is frustrated at supply shortages and has demanded AstraZeneca doses be sent from British plants to make up for a shortfall.

Here’s what we know about the dispute and its potential implications:

– What is the cause of the problem?

AstraZeneca has said initial deliveries to the EU will fall short because of a production glitch – said to be at a hub in Belgium – and it will not be able to meet its supply targets for the first three months of this year.

The Anglo-Swedish company announced initial deliveries in the EU would total approximately 31 million doses, rather than the anticipated 80 million in the first quarter of the year.

With the speed of the UK’s vaccine rollout outstripping other European countries, the EU has suggested doses produced in Europe have been directed elsewhere.

EU Commission president Ursula von der Leyen has now called for an explanation from AstraZeneca for delivery hold-ups, as she insisted the supply orders are “binding” and “the contract is crystal clear”.

What else has the EU said?

EU health commissioner Stella Kyriakides has accused AstraZeneca of a “lack of clarity” and “insufficient explanations”, adding “the answers of the company have not been satisfactory” following a meeting on Monday.

She has proposed forcing all drug-makers to register their Covid-19 vaccine exports in advance, so the bloc can keep track of what they are doing.

Following talks on Wednesday, Ms Kyriakides added: “We regret the continued lack of clarity on the delivery schedule.”

Latvian foreign affairs minister Edgars Rinkevics said states could take AstraZeneca to court for breach of supply contracts if it does not honour its delivery schedule.

And Germany’s health minister Jens Spahn supported restrictions on vaccine exports, saying Europe should have its “fair share”.

He added: “I can understand that there are production problems but then it must affect everyone in the same way.”

Has AstraZeneca responded?

The company’s chief executive Pascal Soriot said the contract only committed to meet the EU’s demands to its “best effort”.

In an interview with Italy’s la Repubblica newspaper that was published on Tuesday, he said the EU’s deliveries were delayed in part because the bloc signed its contract three months later than the UK, and therefore EU manufacturing facilities were still catching up

Translated by Politico, Mr Soriot reportedly said the “contract is very clear: Our commitment is, I am quoting, ‘our best effort'”.

He explained that AstraZeneca and its partner Oxford University had signed a deal with the UK Government for 100 million doses three months before the EU deal for 400 million doses was agreed.

In response to the EU demanding their doses were shipped concurrently, Mr Soriot suggested it was a “super stretch goal”, and added: “We said, ‘Okay, we’re going to do our best, we’re going to try, but we cannot commit contractually because we are three months behind UK’.”

What has the UK said?

Prime Minister Boris Johnson said this week he is “very confident” about the UK’s vaccine supply, while Cabinet Office minister Michael Gove insisted there “will be no interruption”.

Government vaccine tsar Nadhim Zahawi also said on Tuesday he is “confident” supply of the Pfizer jab – which is produced in Belgium – will continue.

Asked if the EU could prevent Pfizer vaccines from being exported, he told Sky News: “No, I’m confident that the Pfizer vaccine will be delivered.

“Pfizer have made sure that they have always delivered for us.

“They will continue to do so.”

But will UK supplies be affected?

The majority of the AstraZeneca/Oxford vaccine supply for the UK is manufactured here rather than at the Belgium plant so it is not expected to be disrupted.

But the EU’s threat to impose new rules on all vaccine manufacturers would affect access to the Pfizer vaccine, which is produced in Belgium.

The row would have to escalate further but if the EU went beyond asking for “early notification whenever [manufacturers] want to export vaccines to third countries” and were to impose actual export controls, then it could limit how many reach the UK.

The UK is scheduled to receive 3.5 million doses of the Pfizer vaccine over the next three weeks.

How many doses of vaccine has the UK ordered?

The UK Government has so far secured 40 million doses of the BioNTech/Pfizer vaccine, 100 million of the Oxford/AstraZeneca jab and 17 million from Moderna – the most-recently approved vaccine but supplies of it are not expected to arrive until spring.

The UK has also secured 60 million doses of the Novavax jab – to be produced on Teesside – with the hope that the Medicines and Healthcare products Regulatory Agency will approve it for use within weeks.

How many doses does the UK currently have?

The UK Government has not published figures publicly on how many doses are currently available.

But with First Minister Nicola Sturgeon facing sustained criticism about the vaccination rollout in Scotland seemingly moving at a slower pace than in other parts of the UK – purportedly due to vaccinating higher proportions of care home residents first – she has suggested she could soon reveal supply figures.

Ms Sturgeon said on Thursday: “I think we will just go back to publishing the actual supply figures from next week, so that we all have transparency around that.”

We’ve got to ensure we continue to have national security of supply

The Scottish Government did – briefly – publish the vaccine doses it had access to, but retracted the documents at the request of the UK Government over apparent concerns about other countries knowing how much is being supplied.

During his visit to Scotland on Thursday, the Prime Minister was asked about the possibility of more data being published.

He said: “We’re in favour of the maximum possible transparency that is compatible with security of supply. That’s the crucial thing, we’ve got to ensure we continue to have national security of supply.”

How is the rollout progressing in the UK?

As of Thursday, official figures showed 7,447,199 people in the UK had received a first dose of either the Pfizer or AstraZeneca vaccines.