The developments came after the government said it was cutting the isolation period required for positive cases and Wales 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 advising offering a primary course of the vaccination 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, aiming to offer a third jab to all adults by the end of the month.

The variant is now the dominant strain of the virus across the country - already one of the hardest hit in Europe, with a death toll of 147,573 - as it registers daily cases at record levels.

Officials 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, the devolved government in Wales announced a raft of new curbs from December 26, including limiting socialising in pubs, cinemas and restaurants to groups of six people or less.

Two-metre distancing will return in public places, while pubs and other licensed premises will be table service only and staff will have to collect contact tracing details and masks will be required once again.

Large events will essentially be banned, with the maximum permissible number of people allowed to gather indoors set at 30, and outdoors at 50.

It follows Scotland unveiling new 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.

Antiviral drugs deal

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.

eNCA