Britain is facing the "biggest wave of infections" it has ever seen as Covid restrictions are lifted today, a scientific adviser to the government has warned.
Daily cases surged past 50,000 last week for the first time since mid-January but ministers have pushed ahead with Freedom Day, saying there is "no good time" to lift lockdown.
Both scientists and the government have agreed that double vaccination weakens the link between infection and serious illness of death.
But experts have urged people to remain cautious, with face masks still recommended on public transport and other crowded spaces.
England's chief medical officer Chris Whitty also warned that the new freedoms, which Boris Johnson previously said he wanted to be "irreversible", may need a rethink in August.
Professor Andrew Hayward, a member of the Scientific Advisory Group for Emergencies (Sage), told Sky News on Monday: "If we have uncontrolled transmission then we will have an extraordinary high number of cases.
"There's already at the moment about one in 100 of us carrying the infection; at the height of the pandemic it got to about one in 50.
"We would expect to be above that and remain high for a long period of time.
"And so, even if only a very small proportion of people who are infected die, a very small proportion of a huge number is still a very big number and an even higher number of hospitalisations."
"So I think this remaining cautious is really a key thing in this unlocking of legal restrictions," he added.
Prof Hayward added: "We are heading into the biggest wave of Covid infection that we have ever seen.
"Even though the vaccine will substantially reduce the number of deaths and hospitalisations, it's still likely that we will see somewhere in the low tens of thousands of deaths even if we are cautious.
"And that could move into the mid and high tens of thousands of deaths if we just went back to normal activity."
It comes as Boris Johnson prepares to hold a Covid press conference remotely today to mark the lifting of lockdown as he isolates after getting pinged by the NHS app.
The Prime Minister came under fire last week after claiming he did not have to self-isolate after coming into contact with Covid-infected health secretary Sajid Javid.
No 10 initially announced that Johnson and chancellor Rishi Sunak were taking part in a pilot workplace scheme that involved daily testing instead.
But after a backlash, the PM U-turned in a video posted on Twitter, confirming that he would stay at Chequers and conducting meetings virtually.
