Doses of Covid-19 vaccine will be diverted to parts of the UK where there is a shortfall over concerns that supply issues are creating a two-speed delivery.
British Health Secretary Matt Hancock said doses would be sent where they were needed most after complaints that people over 80 in some areas have not yet been inoculated.
On Monday, Work and Pensions Secretary Therese Coffey said that "something isn't quite right" about the vaccination programme.
Some people felt “distressed and annoyed” that elderly people were being left behind, she said.
Ms Coffey, Conservative MP for Suffolk Coastal, suggested that people in her constituency over the age of 70 were called up to be immunised before those over 80 and 90.
She said her constituency had mostly received the Pfizer/BioNTech vaccine so far, which was "more challenging to distribute, especially in a rural area" because of the need to store it in ultra-cold conditions.
Maggie Bennett, managing director at Northbroke House on the Isle of Wight, said the fact the Pfizer shot needed to be kept at low temperatures was a problem.
"What was promised to us at the beginning was the Pfizer vaccine, which is difficult to store and distribute," she told the Guardian.
“It wasn’t the most ideal type of vaccine to bring into the care home and that was the difficulty the GP surgeries were having. It wasn’t a lack of motivation, rather … the practicalities of getting it out. A lot of our residents succumbed to it when they might not have done.”
Some vaccine centres were told that they will not get further supplies their vaccination rate is ahead of other areas. Some have had to cease all vaccinations this week because doses that they were expecting are being sent elsewhere.
Mr Hancock, who will go into self-isolation on Tuesday after a Covid alert, said: “We're prioritising the supply of the vaccine into those parts of the country that need to complete the over 80s."
Mr Hancock said he would be working from home until Sunday as a close contact of someone who received a positive test result.
The health secretary's self-isolation began as the Office for National Statistics (ONS) found an estimated one in eight people in England had antibodies against coronavirus in December, suggesting they have had Covid-19 previously.
The ONS said an estimated 12.1 per cent of people aged 16 years and over in England had antibodies last month.
Welsh First Minister Mark Drakeford said the vaccine supply had to last until February to prevent "vaccinators standing around with nothing to do".
But he said that “nobody is holding back vaccines” after his remarks prompted concerns.
Mr Drakeford's spokesman said the distribution of the Pfizer/BioNTech vaccine would be organised in a way that avoided waste.
“The Pfizer vaccine comes in large packs, which cannot be split and must be stored at ultra-low temperatures – at minus 70°C. There are only two centres in Wales where we can keep them at this temperature," he said.
"Once removed from storage, the vaccine lasts five days. Every dose wasted is a vaccine which cannot be given to someone in Wales. Health boards are receiving all the doses of Pfizer they can use.”
Meanwhile, the British Medical Association in Scotland said that supply of doses to GPs was "quite patchy".
"The current problem lies with the next priority group, which is the 80-plus group, which GPs in Scotland are set to vaccinate because the supply of the vaccine so far has been quite patchy," said Dr Andrew Buist, chairman of the Scottish general practitioners committee at the association.
"Some practices have a good supply, some have had none so far."
More than 4.2 million have had their first shot of vaccine in the UK. Authorities aim to vaccinate 15 million people in the top four priority groups by mid-February.
The data shows Northern Ireland is having the most success in administering doses, followed by England. Scotland and Wales lag far behind.
The vaccination rate in London is also a cause for concern. Only 367,000 people have been given a shot in the city, compared with 700,000 people in the Midlands.
On Sunday, nearly 100,000 fewer people were inoculated than on Friday, but the UK government did not say whether the lower figure was caused by a supply issue or a delay in weekend reporting.
Last week, Pfizer said it would reduce vaccine deliveries to EU countries temporarily while it upgraded production capacity. The company said the move did not affect the UK.