Britain will see a significant reduction in the amount of vaccines available from March 29, marring news that as of Tuesday over 25 million people in the UK had received their first dose of a Covid vaccine.
The prospective cut in supply was revealed on Wednesday in a letter sent around the National Health Service.
"The Government's Vaccines Task Force have now notified us there will be a significant reduction in weekly supply available from manufacturers beginning in week commencing March 29, meaning volumes for first doses will be significantly constrained," the letter said.
"They now currently predict this will continue for a four-week period, as a result of reductions in national inbound vaccines supply."
UK Health Secretary Matt Hancock dismissed the revelation in cursory fashion.
"We regularly send out technical letters to the NHS to explain the ups and downs of the supply over the future weeks, and what you're referring to is a standard one of those letters," he said at the daily Covid press briefing.
He said he retained confidence that current targets would be met.
"We're on track to meet the target of offering to all groups one to nine on the 15th of April - I mean if you think about it it's currently the middle of March, and we've already been able to open the to invite all over 50s.
"You'll see the letter refers to the focus that's needed on the particularly vulnerable groups, so that's what we're going to be doing to protect as many people as possible."
Mr Hancock's sanguine responses were calculated so as not to detract from the UK reaching the 25 million first dose milestone.
"This explains why deaths from Covid in this country are now thankfully falling so fast, they're down by over a third in the last week, again," he said.
"And all of this underlines how important it is that when you get the call, you get the jab."
He called the inoculation drive a "national mission" and sought to claim some credit, saying it had been an "honour to play my part".
It was unsurprising that Mr Hancock opted for such self-aggrandisement given the withering criticism levelled at him on Wednesday by Boris Johnson's former chief adviser Dominic Cummings.
The self-styled Svengali told MPs that the Department of Health was a "smoking ruin" under Mr Hancock's stewardship - and that the UK's vaccine programme was moved from under the health secretary's auspices following the personal protective equipment shortage that beset the NHS last year.
Asked to comment on Mr Cummings' remarks, Mr Hancock was evasive, stating simply that both his department and the Vaccines Taskforce had been "brilliant".
Meanwhile, latest Covid data show the UK recorded 5,758 new cases on Tuesday and 141 deaths, a slight increase on Monday's figures.