A record number of daily coronavirus cases have been reported across the UK for the second day running, with 88,376 infections confirmed on Thursday.
England's chief medical officer, Prof Chris Whitty, said the Omicron variant could rise "incredibly fast", but its peak subside quickly due to boosters.
There was also a record for top-up vaccines with 745,183 third or booster doses being given on Wednesday.
Boris Johnson has urged people to use "caution" in the face of the variant. But the prime minister insisted England was not being put into lockdown by stealth, after some of his own MPs had accused the government of putting hospitality under an "effective lockdown".
Wales has introduced a two-stage plan in response to coronavirus with guidance - such as taking a lateral flow test ahead of socialising - for the Christmas period before legal restrictions come into force on 27 December.
These will include all nightclubs closing, 2m social distancing in offices and other measures to protect customers and staff.
A further 146 deaths within 28 days of a positive test were reported on Thursday across the UK, BBC reported.
Daily cases were up from 78,610 on Wednesday, itself a record, and more than 30,000 up on last Thursday when 50,867 infections were reported.
