Government advisors have pleaded with Brits to be cautious despite lockdown easing today - as they fear the Indian variant could trigger "another big wave".
People in England are allowed to meet indoors in groups of six, stay overnight with friends and family, go on foreign holidays to the "green list" and make their own decisions on hugging as the economy finally begins to recover.
But despite new figures today putting the UK's cost of Covid at £372 BILLION, a string of experts said they will be more cautious than government advice allows.
Prof Adam Finn, of the Joint Committee on Vaccination and Immunisation (JCVI) said scientists still don't know exactly how fast the B.1.617.2 strain transmits - with over 1,300 cases already in the UK.
He told Sky News "mixing people together at this particular point in time... is really actually quite risky."
Prof Finn added: "On a personal level. I'm advising my family and friends to continue to be very careful about making contact with each other until we're clearer about just what's going to happen with this variant over the next two or three weeks." © PARosie Delaney, Isobel Loan and Rebecca Mitchell get their first drink at 00:11 at the Showtime Bar in Huddersfield, West Yorkshire
Prof Finn said it was "perfectly likely" that Boris Johnson could have to tear up plans for ending all restrictions from June 21.
He said: "I really hope that the current concerns around this variant evaporate and that everything goes to plan. But I think we just have to accept the possibility that we're in for another big wave and we will have to change what we're doing."
SAGE member Sir Jeremy Farrar also said he wouldn't meet family and friends indoors "for the moment".
He told BBC Radio 4's Today programme: "I think it is reasonable to just be sensible about knowing where transmission is occurring - mostly indoors, mostly in larger gatherings indoors with lots of different people, different families, different communities - and I would just restrict that at the moment personally."
Sir Jeremy said "I don't think it's unreasonable" to lift restrictions now but added: "This is the most difficult policy decision frankly in the last 15 months or so. It is very very finely balanced." © REUTERSSir Jeremy Farrar said he wouldn't meet family and friends indoors
Business Secretary Kwasi Kwarteng today insisted it was still "very likely" all restrictions will be able to end from June 21.
London mayor Sadiq Khan added he would finally be hugging his mum as he urged residents to cautiously return to pubs.
But Mr Kwarteng added: "People shouldn't be running away, getting too exuberant I suppose. I think we need to be measured and cautious."
Sir Jeremy warned scientists still don't know if the vaccine rollout has "decoupled" infection rates from the number of people ending up in hospital or with 'Long Covid'.
He told the BBC: "That is the key question and to be honest we don't know that today." © NurPhoto/PA ImagesTory minister Kwasi Kwarteng said:
The expert warned "we may have to reverse back" into more lockdown if the Indian or another variant proves resistant to a vaccine - as the B.1.617.2 strain is "becoming dominant in parts of the UK".
A third government advisor, SAGE member Prof Graham Medley, said he would go to a pub or restaurant indoors but only under certain conditions.
He told LBC radio: "If it was suitably organised and it looked okay and was in an area of low prevalence and the clientele was very old [and therefore mostly vaccinated]. fair enough."
It comes after a fourth advisor, SAGE's Prof Mark Walport, told Sky News on Sunday he would be avoiding going indoors in a pub.
He said: "[It is] a question of people making judgments and you know my personal judgment is that I will do things outside as far as possible."
He warned Brits against "tight clinches" adding: "My advice is just because you can do something doesn't necessarily mean you should.
"As far as possible, socialise outside, maintain social distancing, if you are going to hug, hug cautiously."
Boris Johnson has issued a plea for people to use a "heavy dose of caution" as lockdown rules ease further today. © Getty ImagesBoris Johnson appealed for caution as lockdown rules lift further on Monday
Pubs and restaurants will be able to reopen indoors and the ban on foreign travel is lifted, allowing holidaymakers to jet off for some sun for the first time in months.
People will also be allowed to hug friends and family from different households for the first time since Covid restrictions were imposed more than a year ago.
But the Prime Minister urged the public to remain cautious despite the greater freedoms, as concerns mount over the spread of the Indian Covid variant.
Surge testing is being ramped up in hotspot areas and the vaccine rollout is being accelerated to prevent the new strain from derailing the route out of lockdown.
Vaccine first doses are tipped to be rolled out nationally to over-35s later this week and over-30s by the end of the month.
London mayor Sadiq Khan joined pleas for hotspot areas to get vaccines faster for younger groups to stop the Indian variant. © ITVLondon mayor Sadiq Khan joined pleas for hotspot areas to get vaccines faster
He told ITV's Good Morning Britain: "There are four or five boroughs where there do appear to be small clusters of this particular Indian variant.
"What I'm asking the government to do and the fantastic NHS is to in those parts of London, young Londoners to receive the vaccine sooner than in other parts of London."
Some medics - including reportedly in Bolton - have been defying government guidance and offering jabs to younger people who come forward.
But government minister Kwasi Kwarteng refused the pleas, saying today: "We would suggest that people should do it in the correct order, in the right way."
And the JCVI's Prof Finn said there must be a "strategic" approach, adding that when younger people get a jab, "you are of course giving doses to vaccine to one person and those doses are not being given to someone else, either there or in other parts of the country.
"We do need to all work on this together and be joined-up about it." © AFP via Getty ImagesPedestrians walk past re-opened shops and businesses in Glasgow
Reports today claim ministers are pushing more strongly for lockdown to end fully on June 21 - amid claims most of those hospitalised declined a vaccine.
Health Secretary Matt Hancock said yesterday: "In Bolton, where we've seen a number of people in hospital with this new Indian variant, the vast majority of them have been eligible for a jab but not taken the jab."
Chris Hopson, chief executive of NHS Providers, said there were "concerns" about small numbers of older people who are yet to take up their vaccine offer.
"The biggest risk comes from, if there are large numbers of older people who are unvaccinated," he told Times Radio.
"Now the good news is we've done very well with the vaccine take-up but there is a very small number who are eligible for the vaccine, who actually haven't taken it and surprise, surprise, as the Secretary of State was saying yesterday, that's the majority of cases that we are now seeing.
"And as he said there were five people who've had a single dose in hospital, and only one person who's had a double dose - so that does suggest that Sir John Bell is correct when he says that actually the vaccine is really efficacious.
"The real issue is that we know that there are communities of people who haven't been vaccinated and who are eligible - and we know there's a link for example to deprivation, we know there's a link to ethnicity."