Plans to introduce booster jabs to protect against Covid-19 were announced by the government on Tuesday – but millions of people have still not had even one dose.
More than a quarter of the population – some 28 per cent – is currently estimated to be unvaccinated. In numbers, that’s roughly 18.6 million people.
Some two-thirds of the total are under 16 and are, therefore, not currently eligible for the shot.
But some 5.9 million remain unvaccinated despite being offered a jab. So, who are they? A nation by nation analysis by the Press Association news agency gives an indication…
Northern Ireland has the highest proportion of people unvaccinated among the four UK nations.
An estimated 31.5 per cent of the population has not received any Covid-19 shot. Among those aged 16 and above, the proportion is 13.5 per cent but levels vary considerably between younger and older age groups.
More than half of 16 and 17-year-olds (55.8 per cent) have not received any vaccine - the equivalent of around 25,000 people.
Some 27.8 per cent of 18 to 29-year-olds have not had a first dose (77,000 people), while the figure for 30 to 39-year-olds is 22.3 per cent (56,000).
Levels are much lower for older age groups, however.
Just 0.3 per cent of 60 to 69-year-olds are estimated to be unvaccinated, while the number of first doses given to people aged 70 to 79 and 80 and over is greater than the estimated size of the population for both groups.
In England, an estimated 28.2 per cent of the population is unvaccinated - the equivalent of around 15.9 million people.
Among those aged 16 and over, the percentage is around one in nine (11.1 per cent).
But as with the other UK nations, the level of vaccine take-up varies greatly across age groups.
More than a quarter of people in England aged 18-29 (26.9 per cent) have yet to receive one dose, or around 2.3 million individuals.
A further 1.3 million people aged 30 to 39 are still unvaccinated - 17.1 per cent of this age group.
By contrast, only 2.9 per cent of people aged 80 and over are estimated to be unvaccinated, along with 1.8 per cent of those aged 70 to 79.
Of the 15.9 million people in England yet to receive any vaccine, 2.7 million are aged 12 to 15.
Just over a quarter of the population of Wales (25.3 per cent) has not received any Covid-19 vaccine - the equivalent of around 802,000 people.
Among those aged 16 and over, the overall proportion is 9.2 per cent, though this varies considerably across age groups.
Some 31.8 per cent of 16 and 17-year-olds have yet to have a first dose - nearly 26,000 people.
There are also 23.0 per cent of 18 to 29-year-olds who are still unvaccinated (112,000 people) and 22.2 per cent of 30 to 39 year-olds (95,000).
By contrast, just 3.8 per cent of people aged 80 and over have not received any vaccine, while the figure for 75 to 79-year-olds is 3.1 per cent.
There are nearly 145,000 children aged 12 to 15 in Wales.
Scotland is the only one of the four UK nations to have given a first dose of vaccine to more than three-quarters (75.8 per cent) of its population.
It means 24.2 per cent are still unvaccinated, or around 1.3 million people.
Some 8.9 per cent of people aged 16 and over have not received a jab - the lowest proportion of any UK nation.
Looking at specific age groups, 36.1 per cent of 16 and 17-year-olds in Scotland have yet to have a first dose (around 40,000 people), along with 24.5 per cent of 18 to 29-year-olds (205,000 people) and 17.1 per cent of 30 to 39-year-olds (125,000 people).
But the number of doses given to people aged 60 and over is greater than the population estimates for all these age groups.
Some 234,000 children aged 12 to 15 are estimated to live in Scotland.