This comes after the pharmaceutical company announced it would be unable to deliver the agreed upon number of doses to the block, which is already criticised for a slow authorization of different vaccines.
However, that rollout here is set to be lower than initially expected due to the company's unexpected delay in delivering millions of doses of its Covid-19 vaccine to European Union member states.
On Tuesday, NHS England chief Sir Simon Stevens told MPs that the uproar was due to limited supplies of vaccines.
All of Canada's current vaccine doses - from Pfizer-BioNTech and Moderna - are manufactured in Europe, potentially pinching vaccine deliveries even further.
The EU is poised to impose export controls on vaccines leaving the 27-member bloc to ensure there's more supply on the continent.
"She made it clear that she expects AstraZeneca to deliver on the contractual arrangements foreseen in the advance purchasing agreement", said Von der Leyen's spokesman, Eric Mamer.
An EU official has told Reuters AstraZeneca had received an upfront payment of 336 million euros ($408 million) when the EU sealed a deal with the company in August for at least 300 million doses and an option for another 100 million.
For Europe, the lack of supply is particularly galling: doses for third countries are often produced in the European Union, which has spent $3.3 billion on funding the development and production of vaccines.
Business paper Handelsblatt has not retracted the story suggesting that the vaccine might be as little as eight per cent effective among over-65s, a claim based on unnamed political sources which was rejected by the manufacturers and the United Kingdom and German governments on Tuesday.
He then signed an executive order in December demanding US -produced vaccines be prioritized for Americans only and threatened to use the act to halt vaccine exports as well.
In a letter sent to the company on Sunday (24 January), Health Commissioner Stella Kyriakides also stressed the importance of timely delivery of vaccines as set out in the APAs.
The University of Oxford and drug manufacturer AstraZeneca have developed a COVID-19 vaccine.
The AstraZeneca jab is expected to be approved by the EU's medicine's regulator, the EMA, in the next few days.
Following AZ's announcement Friday, European officials were set to meet with AstraZeneca executives on Monday to seek clarification, Reuters reports; one European official had called AstraZeneca CEO Pascal Soriot ahead of the meeting.
This appeared to be an overture by AstraZeneca to try and keep the peace with the European Union as the row over its sudden cut to deliveries escalates, damaging trust between Brussels and the drugmaker.
A subheading noted that Germany's health minister Jens Spahn had been "circumspect" about the claim, without mentioning the ministry's subsequent denial.
But Europe, which invested more than C$4 billion in vaccine development, is demanding the companies fulfil their contracts on time.
"I'm confident of the supply of vaccine into the UK".
