LONDON: Britain recorded 53,945 new COVID-19 cases on Thursday, the highest daily figure since July 17, government figures showed, as the dominant Delta variant spreads and measures come in to curb the Omicron variant of concern.

Cases were up 2.8% over the last seven days compared with the week before, although deaths were down 3% over the same time span.

There were a further 141 deaths within 28 days of a positive coronavirus test recorded on Thursday, down from 171 the day before.

The UK Health Security Agency said that cases were highest in those aged 5 to 9 years old, evidence that cases have risen again in schools after dipping following a half-term break a month ago.

Cases were lowest in the over-80s, who are among the most vulnerable from COVID-19 and have also been prioritised for booster shots.

UK issues call to arms for Omicron booster drive

"As we observe the Omicron variant emerging, the Delta variant continues to circulate at high levels across all age ranges," said Steven Riley, Director General of Data, Analytics and Surveillance at UKHSA.

Prime Minister Boris Johnson, who received his booster shot on Thursday, lifted COVID-19 restrictions in England in July, and is bidding to withstand the winter relying mainly on booster vaccine doses rather than lockdowns.

However, he has reintroduced mandatory mask-wearing in shops and on transport out of concern over the Omicron variant.

There have been 32 confirmed cases of Omicron so far, and Johnson has also introduced travel curbs in order to slow its spread while work is done to understand the full implications of the variant.