UK Prime Minister Boris Johnson on Friday announced England's reopening would go ahead as planned, but expressed concern over the spread in the UK of a strain of coronavirus first detected in India.
Mr Johnson said the new variant could threaten further easing of lockdown measures set for June.
"We will proceed with our plan to move to step three in England from Monday, but I have to level with you that this new variant could pose a serious disruption to our progress and could make it more difficult to move to step four in June," he said.
As a result, Mr Johnson said England would accelerate its Covid-19 vaccination campaign to ensure that all patients over 50 receive second doses.
"It's more important than ever, therefore, that people get the additional protection of a second dose," he said.
"We will accelerate remaining second doses to the over 50s and those clinically vulnerable right across the country, so those doses come just eight weeks after the first dose."
Mr Johnson said the Indian strain could be more transmissible than the previous Kent variant – first detected south-east England in September 2020 – but said data has not shown a significant increase in hospital admissions.
From Monday, restaurants and pubs in England can offer indoor seating for groups of up to six for the first time since November.
Indoor entertainment, such as cinemas, museums and children's play areas can also open, alongside theatres and sports venues. In addition, hugging will be allowed as social distancing measures in private homes are eased.
Meanwhile, Scottish First Minister Nicola Sturgeon said Glasgow and Moray would remain under level three restrictions while the rest of the country would drop to level two next week.
Both areas will initially remain at level three for a week, she said, with a decision made at the end of next week.
