British regulators on Wednesday approved Pfizer's Covid-19 vaccine for use in children aged five to 11, as the country reported more than 100,000 new daily cases for the first time as Omicron surged.
The developments came after the government said it was cutting the isolation period required for positive cases while Wales and Northern Ireland followed Scotland in unveiling new post-Christmas curbs, primarily around hospitality and large events.
Britain's Medicines and Healthcare products Regulatory Agency (MHRA) said it had approved a new lower-dose formulation of the Pfizer-BioNTech shot after finding it was "safe and effective" for children aged five to 11.
MHRA chief executive June Raine said there was "robust evidence to support a positive benefit risk for children in this age group".
The "overwhelming majority" of reported side-effects from the two-shot "age-appropriate" jab related to mild symptoms, such as a sore arm or a flu-like illness, she added.
The Joint Committee on Vaccination and Immunisation, which advises UK health departments on immunisation, said it was now recommending a primary course of the vaccination be offered to some within the age group.
Britain is in the midst of a stepped-up booster campaign, as it tries to minimise the impact of weeks of rising Omicron infections.
On Wednesday the country surpassed 30 million third doses administered as it aims to offer the additional jab to all adults before the end of the year.
The variant is now the dominant strain of the virus across the UK -- already one of the hardest hit in Europe, with a death toll of nearly 148,000 -- as daily cases reach record levels.
It announced 106,122 new infections Wednesday, the highest figure since mass testing began in the summer of last year.
Earlier, the government said people who have tested positive can stop self-isolating after seven days instead of 10 if they have taken two negative lateral flow tests.
Amid the skyrocketing case numbers, it could potentially allow many more to join family Christmas celebrations.
Hours later, devolved governments in Cardiff and Belfast announced new curbs from December 26 -- leaving just England with no imminent restrictions unveiled.
In Wales, socialising in pubs, cinemas and restaurants will be limited to groups of six people or less, while mandatory table service and providing contract tracing details will return.
In Northern Ireland, nightclubs will have to close at 8 pm, alongside guidance to limit contacts with different households.
It follows Scotland announcing renewed rules there Tuesday, which also come into force on December 26 for at least three weeks, and cap attendance at outdoor events at 500.
The move means the pandemic has forced the cancellation of Edinburgh's hugely popular New Year's Eve street party for the second successive year.
However, UK Prime Minister Boris Johnson has resisted calls to impose stricter rules in England over Christmas.
The embattled leader, reeling from weeks of scandals and setbacks -- plus growing discontent in his own party -- has said he wants more evidence on Omicron's severity and ability to evade vaccines.
Meanwhile his government has signed deals to buy more than 4 million courses of two new antiviral drugs-- Pfizer's ritonavir and US rival Merck/MSD's molnupiravir -- to treat Covid-19.
Molnupiravir, sold as Lagevrio, is part of a national trial run by the University of Oxford that people can join if they have virus symptoms.
Britain was the first country in the world to approve it last month and the authorities will make it available to those at high risk of severe illness, such as people with cancer.
Pfizer's pill, marketed as Paxlovid, has yet to be authorised anywhere in the world.
The company said Tuesday that clinical trials showed it reduced hospital admissions and deaths among at-risk people by almost 90 percent, when taken a few days after symptoms began.