Video report by ITV News Political Correspondent Carl Dinnen
The prime minister has urged Britons to stick with coronavirus lockdown restrictions to help ensure the current lockdown is the last, as he looked ahead to revealing a roadmap out of restrictions on February 22.
Boris Johnson said he aims to cautiously lift restrictions in an "irreversible" manner, but conceded he cannot offer a "cast iron guarantee" that England's third national lockdown will be its last.
Mr Johnson welcomed the "unprecedented national achievement" of reaching the 15 million vaccine target, but said now is "no moment to relax", acknowledging concerns of lockdown-sceptical Tory MPs who have been pressing for a swift reopening.
"Although the vaccination programme is going well, we still don’t have enough data about the exact effectiveness of the vaccines in reducing the spread of infection," he said.
The PM said there are "grounds for confidence" that vaccinations reduce Covid-19's spread, but said they are awaiting the "hard facts" before setting out the timetable for easing the lockdown.
He told a the press conference that no decisions had been taken ahead of detailing his "road map", urging people to take any speculation with a "pinch of salt".
He added he wants England's third lockdown to be the last, with progress out of restrictions "to be cautious but also irreversible".
Sir Simon Stevens, Chief Executive of NHS England said the UK is now in its "second sprint" of the coronavirus vaccine rollout after reaching the 15 million target.
The NHS boss welcomed the achievement of vaccinating the top four priority groups, but he warned reaching the milestone does not mean "mission accomplished".
"We've just come through the finishing line of the first sprint," he said, "and now we've got a second sprint between now and April 30 to extend the number of vaccinations given to the higher risk groups of the population before moving onto the marathon."
He told a Downing Street press conference that will involve vaccinating everyone in the country who is eligible, along with the winter flu campaign and potentially a drive to offer booster jabs in the autumn to tackle the emergence of new variants, "if that's what the science suggests is needed".
Mr Johnson confirmed the government had moved to a new target of vaccinating everyone in the top nine most vulnerable groups by the end of April.
Sir Simon said the new vaccination target had been set for the end of April "likely" due to vaccine supply but added that "if supply increases then we think we can go faster".
"Give us the tools for vaccines and we will finish the job," he added.
England's chief medical officer Professor Chris Whitty said there is "reasonable evidence" that booster jabs may be needed after the second vaccine target is reached.
He said: "We may have to do that this year because there are several variants that look very similar to one another in many ways which actually could have slightly reduced - not completely reduced but slightly reduced or in some cases more than slightly reduced - effectiveness from the vaccine.
"In which case we then redesign the vaccine - scientists redesign the vaccine - and that allows us to revaccinate against the new variant."
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