More than 900,000 COVID booster jabs were given out across the UK on Saturday - a daily record.
In addition to the 904,598 people who received a third dose yesterday, 44,599 had their second and 37,492 came forward for their first one.
Another 82,886 coronavirus cases have also been reported in the latest data - down on recent days but much higher than last Sunday's total of 48,854.
There have been 45 more deaths within 28 days of a positive COVID-19 test, which is down on yesterday's 125, and also on the 52 reported this time last week.
The average number of deaths over the past seven days is down 6.5% on the previous week, but infections are up by more than 51% and hospital admissions are up by 8.1%.
Latest data says there are 7,611 COVID-19 patients in hospital, with 875 on ventilators.
'Actual number of infections will be significantly higher'
Health Secretary Sajid Javid told Sky News the "actual number of infections will be significantly higher than case numbers suggest" because not everyone will be taking a test and there is a lag for people to get their results.
Appearing on Trevor Phillips on Sunday, Mr Javid did not rule out plans for a two-week circuit breaker after Christmas, saying the government will "do what is necessary".
He added that ministers are discussing the latest data "almost on an hourly basis" with scientific advisers.
Daily Omicron cases
Another 12,133 Omicron cases were reported by the UK Health Security Agency.
This brings the total confirmed cases of the variant in the UK to 37,101.
The health secretary said the new variant is spreading "very, very quickly" - but added that not enough is known about it at the moment.
Warnings issued by medical experts
Professor Sir Mark Walport, who is a member of the Scientific Advisory Group for Emergencies (SAGE), warned infections are "rising fast" and more time is needed for recently administered vaccines and boosters to take effect.
He said: "We need to act to hold down the rate of hospital admissions, reduce the pressure on the workforce - and of course a lot of people are off sick at the moment.
"And most importantly of all, give people the chance to get vaccinated, to get boosted, and allow time for those vaccinations to have effect."
Projections considered by the SAGE advisory committee on Thursday show that hospitalisations are expected to increase from their current level of 900 a day to between 1,000 and 2,000 a day by the end of the year.
They are likely to peak in January at well over 3,000 every day, even with the current Plan B restrictions.