The head of NHS England has warned that Covid-19 could still "wreak more havoc" as England prepares for some lockdown restrictions to ease from tomorrow.
Professor Stephen Powis said Brits should not "squander the gains" made against coronavirus as the rule of six returns and more freedoms will be allowed outdoors.
Citing concerns about new Covid variants, the NHS boss said "enormous progress" had been made, but it "does not mean job done".
He issued the warning ahead of groups of up to six, or two households, being able to socialise in parks and gardens once more as outdoor sports facilities reopen and the stay-at-home order ends in England on Monday.
Earlier, Boris Johnson said he is wary of the prospect of rising coronavirus infection rates, but sees "absolutely nothing in the data" to halt the easing of the lockdown.
The Prime Minister acknowledged cases could again spiral as restrictions are relaxed but said the "key difference" this time is that the rise in prevalence should be "sufficiently mitigated" by the successful vaccine rollout.
Professor Powis said the prospects "look immeasurably brighter and more positive" but added that people should still be careful despite the easing of lockdown restrictions.
He wrote in the Sunday Telegraph : "We've made enormous progress that we need to build on and not squander the gains we've made.
"We need to hold our nerve and drive for the line, so everyone can get back safely and soon to our normal lives."
Meanwhile, the UK was planning to offer 3.7 million jabs to Ireland, partly to help ease lockdown restrictions in Northern Ireland, according to the Sunday Times.
It would be the first time Britain exported jabs to the EU and the newspaper reported a Cabinet minister saying it would be a "poke in the eye" for Brussels amid a row over supplies.
It comes as Culture Secretary Mr Dowden confirmed the Moderna vaccine will start arriving in the UK at the end of this month, three months after it was approved by the MHRA regulator.
He told Sky News today: "We do expect Moderna to come later this month."
He reiterated: "We don’t get into the details of supply chains, but the Health Secretary has indicated that he would expect later this month we’d start to see Moderna."
During a discussion at the Conservatives' virtual spring forum on Saturday, the PM said that a "third wave" is being witnessed in parts of Europe and "bitter experience" has taught him that this could hit the UK "three weeks later".
But he added: "There's lots of promising evidence that a lot of people who could be vulnerable are now protected against death and serious disease, that's my hope, my hunch."
Mr Johnson remained optimistic that his road map to easing England's restrictions can continue, saying there is a "good chance" of allowing non-essential retail reopening on April 12, when hairdressers are also earmarked to reopen.
"In just a few days' time, I'm finally going to be able to go to the barbers," he said in a subsequent speech.
"But more important than that, I'm going to be able to go down the street and cautiously, but irreversibly, I'm going to drink a pint of beer in the pub.
"And as things stand, I can see absolutely nothing in the data to dissuade me from continuing along our road map to freedom, unlocking our economy and getting back to the life we love."
Government data up to Friday showed that 29,727,435 people in the UK have received a first jab, a rise of 411,305 on the previous day.
The Government said a further 58 people had died within 28 days of a positive test for Covid-19 as of Saturday, bringing the UK total to 126,573.
In Wales, lockdown restrictions were eased when the "stay local" requirement was dropped on Saturday and people were allowed to stay in self-contained holiday accommodation.
A relaxing of England's lockdown will take place on Monday when the "stay home" order ends, and groups of up to six people, or two households, are able to meet outside.
