Britain said on Tuesday it was confident of receiving all the vaccine doses it has ordered, despite supply chain issues sparking a political backlash in Europe.
The UK is racing to meet a target of vaccinating nearly 15 million people by the middle of next month, and the entire adult population by the autumn.
However, fears are growing that the initially impressive rollout could be threatened by supply issues in Europe and possible action by the European Union, which is facing concerns over its supply.
British-Swedish pharma group AstraZeneca, whose jabs are already being rolled out in the UK, said on Friday it would not meet its contractual delivery commitments to the EU because of "reduced yields".
Earlier this month, Pfizer, whose jabs are already being used in the EU and UK, said it would reduce all deliveries in January and February as it tries to scale up production.
The delays have infuriated the EU, which has been vaccinating at a slower pace so far and warned on Monday it would take "any action required to protect its citizens and rights".
EU health commissioner Stella Kyriakides said on Monday she would require drug firms to notify EU officials of vaccine exports out of the bloc, except for humanitarian deliveries.
That could imperil some deliveries to Britain, which left the EU last year.
But vaccines minister Nadhim Zahawi told Sky News: "I'm confident that the Pfizer vaccine will be delivered."
He said Pfizer had made "a very important announcement on the equitable supply of the whole world", which he was sure they would honour.
Zahawi also warned in an interview with Times Radio that so-called vaccine nationalism was "the wrong way to go".
"We need to work together rather than begin to muse policies of vaccine nationalism," he said.
Britain, which has secured early access to 367 million doses of seven of the most promising vaccine candidates, began its rollout in December.
It has administered more than 6.5 million doses.