Britain insisted Thursday that its plan to ease coronavirus lockdowns in the coming months remains on track, despite a vaccine supply shortfall from India which will hit the inoculation drive in April.
The state-run National Health Service in England has warned in a letter to local vaccination centres that doses will be "significantly constrained" from March 29 for four weeks.
The next phase of the inoculation campaign, covering people in their 40s, will have to be suspended until May, the letter said.
The problem is linked to a delay in getting new jabs from the Serum Institute of India by UK-based drugs giant AstraZeneca -- the same company whose supply issues have caused anger in the European Union.
"Five million doses had been delivered a few weeks ago to the UK and we will try to supply more later, based on the current situation and requirement for the government immunisation programme in India," a spokesperson for the institute said.
But British Prime Minister Boris Johnson -- who plans to visit India next month -- denied there was any export ban in place by the government in New Delhi, as it grapples with its own surge in Covid-19 cases.
"The Indian government hasn't stopped any exports. There is a delay, as there is very frequently in vaccination programmes," he told a news conference, thanking the institute for its "heroic" performance so far.
- 25 million vaccinated in UK -
The UK government's phased easing of its third lockdown in England, which was imposed in January amid a winter surge in caseloads of Covid-19 and resulting deaths, hinges on the success of the inoculation drive.
"There is no change to the next steps of the roadmap," stressed Johnson, who is due to get his own AstraZeneca jab on Friday.
"We've now vaccinated over 25 million across our entire United Kingdom -– more than the entire population of many countries -- and our progress along the road to freedom continues unchecked."
Health Secretary Matt Hancock earlier said supply constraints were compounded by the need for Britain to retest a batch of 1.7 million doses already received.
But he insisted to parliament: "To any member of the public who is watching, what I would say very clearly is that the vaccination programme is on track to meet the targets that we have set out."
The government said it was sticking to its target of offering a first dose to every adult by the end of July.
- EU threat -
AstraZeneca's jab, developed with Oxford University, provides the bulk of Britain's campaign and a large portion of its supply has been produced by the Serum Institute of India, the world's biggest vaccine maker.
AstraZeneca said its "UK domestic supply chain is not experiencing any disruption", but made no mention of possible problems in India.
Britain's current other vaccine provider is Pfizer, which denied any issues with its UK delivery schedule.
Hancock said that jabs from a third approved supplier, Moderna, are expected "in the coming weeks".
The supply issues are another headache for AstraZeneca after its jab was suspended in several EU countries, pending a review by the European Medicines Agency following isolated cases of blood clots and brain haemorrhages.
The EMA restated its approval for the vaccine on Thursday, as did Britain's own drugs regulator.
The EU meanwhile threatened on Wednesday to invoke emergency powers to block European exports of Covid-19 vaccines to ensure "reciprocity" with other suppliers, urging Britain to send Europe more jabs.
Britain reacted angrily to the threat, with Foreign Secretary Dominic Raab suggesting the bloc was engaging in "brinkmanship".