The number of new coronavirus infections in the UK have hit a near two-month high as regulators authorised the use of the single-dose vaccine from Johnson & Johnson.
The latest authorisation, which takes the number of vaccines in the UK's armoury to four, comes amid growing speculation that the new variant of the virus first identified in India may prompt the UK government to delay its next planned easing of lockdown restrictions in England.
Government figures showed that another 4182 new confirmed cases were reported across the UK, the highest daily figure since April 1.
The cases bring the total number of confirmed infections reported over the past seven days to 20,765, a 24 per cent increase from the previous week.
The rise prompted scientists to say the UK is now in the midst of a third wave of the pandemic.
The number of cases remains well below the daily high of nearly 70,000 recorded in mid-January, during the peak of the second wave, but the upward trend has raised questions about the UK government's plan to lift all remaining social restrictions on June 21.
The government, which has lifted restrictions in stages and allowed pubs and restaurants to resume indoor service last week, has said it will make a decision on the next planned easing on June 14.
The variant identified in India is believed to be responsible for up to 75 per cent of new cases in the UK and more transmissible than the previously dominant strain of the virus.
Critics argue that the Conservative government is to blame for the variant's seeding in the UK.
They say officials acted too slowly to impose the strictest quarantine requirements on everyone arriving from India, which is in the midst of a catastrophic resurgence of the virus.
Many scientists say the increase in cases is no surprise but that the rapid roll-out of vaccines will provide a firewall in a country that has Europe's highest virus-related death toll at more than 127,500.
As of Friday, 58 per cent of the UK population has received at least one vaccine dose and about 35 per cent have had two shots.