The UK Health Security Agency allowed on Wednesday the use of smaller doses of Pfizer's COVID-19 vaccines in children aged 5 to 11 who are at a higher risk from COVID-19.
"Children aged 5 to 11, who are in a clinical risk group or who are a household contact of someone (of any age) who is immunosuppressed, should be offered a primary course of vaccination," it said.
The regulator said a third of the adult dose will be administered twice with an interval of eight weeks.
The agency also recommended giving booster shots to teenagers aged 16 to 17 and at-risk children aged 12 to 15 in a bid to ramp up the revaccination campaign.
The UK's daily cases soared to over 90,000 on Tuesday as the Omicron variant continued to spread across the country, just days before Christmas. Prime Minister Boris Johnson said no new restrictions were forthcoming.