The UK recorded the most coronavirus cases in a day since mid-February, amid warnings the current wave of infections driven by the highly transmissible delta variant may still be weeks from peaking.

More than 11,000 new cases of the disease were reported on Thursday, along with 19 deaths, according to the Department Health. A study by Public Health England showed infection rates increasing across all age groups, but are highest among people aged 20 to 29. Separately, the government said eight in 10 adults have now had their first vaccine dose.

The data illustrates how the delta variant, first identified in India, upended the government's plan to lift remaining pandemic restrictions this month. Prime Minister Boris Johnson announced a four-week delay on Monday to allow more adults to receive a second dose of the vaccine, which data show significantly increases protection against the new strain.