"We expect this announcement will have a direct and immediate impact not only on our national vaccination plans, but also in our citizens' trust in vaccines against COVID-19," the letter said.
The EU is grappling with a slow vaccine rollout caused by supply problems and by repeated changes in the use of the AstraZeneca shot, which have increased vaccine hesitancy.
"AstraZeneca confirmed to us not being under any obligation to other parties that would impede to complete the fulfilment of its obligations" to the EU, the Commission spokeswoman said when asked about Hancock's statements.
Under the EU contract, AstraZeneca committed to supplying vaccines produced in four European factories, two of which are in Britain: Oxford Biomedica and Cobra Biologics.
Sudan became the first country in the Middle East and North Africa region to receive vaccine doses through the COVAX facility this month when 828,000 doses of the shot produced by AstraZeneca arrived in the East African country.
AstraZeneca said results it published on Monday in which the vaccine had demonstrated 79% efficacy were based on an interim analysis of data through Feb. 17, and it would now "immediately engage" with the independent panel monitoring the trial to share its full analysis.
AstraZeneca will publish up-to-date results from its major US COVID-19 vaccine trial within 48 hours.
On Saturday the EU Commission had asked Italy's prime minister to inspect some batches of vaccines at a production plant in Anagni, south east of the capital Rome, the official added.
The checks were carried out by the Italy's Carabinieri military police between Saturday and Sunday, the official said.
"In the morning I got a report... showing that there are more and more people willing to get vaccinated and also to get vaccinated with the AstraZeneca vaccine," Mateusz Morawiecki told reporters.
"This shows that we made the right decision not to suspend vaccinations with AstraZeneca. There are definitely more people willing to be vaccinated with this vaccine."
One reason for the wastage is that, while many urban vaccination centres have been crowded, some rural sites have had to nudge people to get shots due to a lack of awareness among the public, which can lead to vaccine wastage.
Once a vaccine vial is opened, doses need to be administered within four hours, making it vital for health workers to coordinate the flow of recipients.
The European Medicines Agency is investigating reports of 30 cases of unusual blood disorders out of 5 million recipients of the vaccine in the region.
"We have no signal of concern in this regard," Vinod Kumar Paul, who heads a government committee on vaccines, told a news conference, adding that experts in India had looked into the issue.
The move comes after Austria stopped using a batch of AstraZeneca shots while investigating a death from coagulation disorders and an illness from a pulmonary embolism.
"It is currently not possible to conclude whether there is a link. We are acting early, it needs to be thoroughly investigated," Health Minister Magnus Heunicke said on Twitter.
The vaccine was approved under Canada's interim order system, which allows for accelerated approvals similar to the US Food and Drug Administration's emergency use authorizations.
Canada has secured access to 20 million doses of the AstraZeneca vaccine.
If we are talking about the decision of the medical council, we expect it in the coming days or possibly hours, but it is clear that elderly people will not be vaccinated with this shot.
"We are waiting for a clear recommendation from the medical council and then... we will take a decision."