BORIS Johnson has insisted now is “no moment to relax” in the fight against coronavirus despite the UK wide mass vaccination reaching the 15 million jags target as he admitted that while he wanted this to be the final lockdown, he could not guarantee it.

Yet despite the caution, the Prime Minister said he was optimistic about the future as science was showing how it was getting the upper hand in the battle against Covid-19.

At a Downing St press conference, Mr Johnson welcomed the “unprecedented national achievement” of vaccinating 15 million of the most vulnerable people in the UK ahead of the target deadline on Monday.

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But he insisted this was now “no moment to relax” as UK ministers reviewing coronavirus restrictions in England come under pressure from lockdown-sceptical Tory MPs to commit to a swift reopening.

The PM said there were “grounds for confidence” that vaccinations did reduce Covid-19’s spread but he made clear the Government was waiting on “hard facts” before setting out the timetable for easing the lockdown south of the border.

He told the press conference that no decisions had yet been taken ahead of detailing his “road-map” on February 22, urging people to take any speculation with a “pinch of salt”.

“We want this lockdown to be the last,” declared Johnson but stressed: “And we want progress to be cautious but also irreversible.”

But, while saying he was “increasingly optimistic” about the possibilities to ease restrictions, he acknowledged he could not guarantee it would be the last lockdown.

“I’m very hopeful that we’ll be able to go ahead and open things up, but to say I can give an absolute cast iron guarantee that we won’t face further difficulties and have to think harder and deeper about some problems, no at this stage I can’t.”

The PM did not completely rule out the prospect of a domestic “vaccine passport” but suggested, rather, that mass vaccine coverage and the use of rapid lateral flow testing was the favoured approach to reopen “the toughest nuts to crack” such as nightclubs and theatres.

Mr Johnson stressed that infections remained “very high” and the NHS was still facing extraordinary pressures, while pointing out that, although more than 90% of over-70s had been vaccinated, some 60% of hospital patients with Covid-19 were under that age.

“We have to keep our foot to the floor,” he said, as he called for people to be “optimistic but also patient” about the situation.

He said his plan next week would include “as much as we possibly can about the route to normality, even though some things are very uncertain”.

Earlier, Mr Johnson said no decisions had been made on whether all pupils in England could return to school at the same time on March 8 after reports suggested a staggered approach might be taken with secondary schools going back a week later than primaries.

The successful rollout of the vaccine programme is leading to increased pressure from the Covid Recovery Group[CRG] of Conservative MPs to end restrictions quickly.

Over the weekend, more than 60 CRG members signed a letter calling on the PM to commit to a firm timetable ending with the lifting of all legal controls by the end of April.

Earlier, Mr Johnson said he would aim to give target dates for restrictions being eased when he set out his plan next Monday but stressed that “we won’t hesitate” to delay plans if infection rates made it necessary.

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Professor Stephen Reicher, a scientist advising the Government’s Covid-19 response, warned that giving dates for lifting restrictions could be damaging if they were not met.

The member of the Scientific Pandemic Insights Group on Behaviours said: “If things don’t happen on that date then people begin to be hopeless and helpless.

“You begin to have a sense of ‘look, there’s nothing we can do’ and that sense of helplessness is very damaging psychologically.

“It’s far more constructive to say to people ‘this is what we can do to get infections down’, to give people something active to do.”

Mr Johnson urged people entitled to a jab to accept them after Matt Hancock, the UK Government’s Health Secretary, suggested around a third of social care staff still had not received a vaccine, despite being one of the prioritised groups.

The PM’s spokesman said the Government favoured encouraging care home staff to come forward and accept jabs rather than employers making them mandatory, echoing vaccine minister Nadhim Zahawi, who said such a move would be “discriminatory”.

In other developments:

*Government figures put the number of people to have received a vaccine at 15,300,151 – a rise of 237,962 on the previous day;

*a further 230 people had died within 28 days of testing positive for Covid-19 as of Monday, bringing the official UK total to 117,396;

*a Warwick University study suggested schools did not play a significant role in driving the spread of Covid-19 in the community and

*the first international travellers required to isolate for 10 days at Government-designated quarantine hotels arrived at Heathrow Airport on Monday morning.

The passing of the 15m vaccinations mark paves the way for the next phase of the rollout, covering the next five priority groups, including the over-50s.

NHS England Chief Executive, Sir Simon Stevens, said the end of April target to vaccinate the estimated 17m people in the next five groups had been set due to the “likely vaccine supply” but added that “if supply increases, then we think we can go faster”.