Mr Hancock admitted the emergence of the Indian variant, which has become dominant in the United Kingdom, had made the "calculation" on whether to proceed with unlocking this month "more difficult" as he revealed the latest scientific advice is that the mutation - also known as the Delta variant - is 40% more transmissible than the Kent strain.
The Health Secretary, pressed on whether the June 21 removal of restrictions could be postponed if the Indian variant data "gets bad", told the BBC's Andrew Marr Show: "We are absolutely open to doing that if that's what needs to happen". Public Health England said last month that research showed double vaccination was similarly effective against both the Kent and Delta variants. "That means that it is more hard to manage this virus with the new Delta variant", Health Secretary Matt Hancock told Sky News, referring to the Indian strain by its formal designation.
"Then, once we have got everybody having had their second dose, then you will get this protection that we are seeing at the moment among older people, you'll get that protection throughout the whole adult population".
Still, U.K. Prime Minister Boris Johnson said last week that nothing in the data suggested a reason to derail the plan to end the lockdown, while cautioning that he would move prudently on reopening.
"Everybody must go and get their second jab though because the first isn't as effective on its own".
He said: "The majority of people going into hospital right now are unvaccinated".
"This week we will be opening up vaccines to the under-30s and so we are getting a step closer to the point when we have been able to offer the vaccine to all adults in this country", he said.
WHO warns of June-July Covax doses shortfall
Biden has committed to providing other nations with all 60 million domestically produced doses of the AstraZeneca vaccine. That vaccine has yet to be authorized for use in the USA but is widely approved around the world.
Hancock said the 40 percent figure came from the government body of scientific advisers, SAGE.
"So the good news is that the vaccine still works just as effectively".
Three out of the four tests are now being met, with the risk assessment from the Delta VOC the only unknown factor ahead of June 14 when the government is expected to confirm whether the unlocking roadmap will stay on track for June 21.
The senior Government minister also implied that social distancing could continue beyond the final stage of the Prime Minister's road map.
"The way we are looking at this is step four [of the roadmap] involves the removing of the remaining social restrictions like the rule of six and some of the business closures which are still there".
Meanwhile, there were 203,613 first vaccine doses administered on Saturday, taking the total to 40,333,231, and 473,378 more second jabs were given, taking that total to 27,661,353.
The so-called Delta variant, which appears to spread more rapidly than previous United Kingdom variants, is now the dominant COVID strain in Britain, fueling a surge in cases.