At least 6.1 million booster doses of Covid-19 vaccine have been delivered in the UK, new figures show.
An estimated 5,235,928 doses had been delivered in England as of October 24, along with 511,807 in Scotland and 51,053 in Northern Ireland.
In Wales, 322,591 booster doses had been delivered as of October 21 – the latest figure available.
It means at least one in eight people in the UK who have received a first and second dose of vaccine are likely to have also received a booster.
The figures have been published by NHS England, Public Health Scotland, Public Health Wales and the Northern Ireland Department of Health.
The figure for England includes a small number of third primary doses of vaccine, NHS England said.
Wales continues to lead the other nations in the proportion of double-jabbed people who have also received a booster, at 14.4%, according to analysis by the PA news agency.
This is despite the data for Wales running several days behind the other three nations.
The latest figure for England is 13.7%, with 13.1% for Scotland and 4.1% for Northern Ireland.
A breakdown by age group suggests nearly six in 10 double-jabbed people aged 80 and over in England have now had a booster (58%), along with nearly half of eligible 75 to 79-year-olds (47%).
The equivalent figures for Wales, as of the end of last week, were 47% and 31%.
Data on booster take-up among age groups in Scotland and Northern Ireland is not yet available.
In north-west England, north-east England and Yorkshire, 15.0% of all double-jabbed people are estimated to have received a booster – the highest proportion for any of the regions in England.
London has the lowest proportion, at 12.1%.