Five million doses of the Moderna coronavirus vaccine have been ordered by the UK, the health secretary has announced.
Matt Hancock said preliminary trials showing it to be 94.5% effective were "excellent news" and that, if it proves safe, the jabs can start to be rolled out across the country by spring 2021.
"We can see the candle of hope," he declared, but cautioned that people must keep following COVID-19 restrictions.
The vaccine, which Moderna produced in collaboration with the US government's "Operation Warp Speed", is particularly attractive given it can be stored relatively easily.
It has been shown to last for up to 30 days in household fridges, at room temperature for up to 12 hours, and remains stable at -20C - equal to most household or medical freezers - for up to six months.
That would make storage and transportation of it more attractive than a Pfizer/BioNTech vaccine, which was last week announced to be 90% effective at protecting people from coronavirus but needs to be stored at around -70C.
So far, the UK government has secured access to seven candidate vaccines - totalling more than 355 million doses.
Mr Hancock said Moderna's progress was an "encouraging step forward", though cautioned: "This is preliminary, the safety data is limited and their production facilities are not yet at scale."
Addressing the nation from a Downing Street news conference, he added: "Great advances of medical science are coming to the rescue.
"While there is much uncertainty, we can see the candle of hope and we must do all we can to nurture its flame.
"But we're not there yet; until the science can make us safe we must remain vigilant and keep following the rules that we know can keep this virus under control."
Asked by Sky News if the government should have acted earlier to secure more doses from Moderna, Mr Hancock said he had ordered different types of vaccine from other companies already "to make sure that we have a good spread".
The Moderna results were hailed by Prof Jonathan Van-Tam, England's deputy chief medical officer, also speaking from Number 10.
"Do I feel more encouraged?" he asked.
"It's brilliant news, absolutely brilliant. It's the second penalty now that's also gone into the back of the net, so we're starting to feel in a better position."
But on a more sombre note, Dr Susan Hopkins, the interim chief medical officer of Test and Trace, said that when England's second national lockdown ends on 2 December, the rules could be tougher than they were when the country went into it.
"We will have to think about strengthening them in order to get us through the winter months until the vaccine is available for everyone," she said, adding: "We see very little effect from Tier 1."
Also confirmed by the government on Monday was the creation of two new "megalabs" to boost coronavirus daily testing by 300,000 a day each - due to be up and running early next year.
Prime Minister Boris Johnson was unable to announce them himself however because he has gone into self-isolation, after he came into contact with a Tory MP at a meeting in Downing Street last week who later tested positive for COVID-19.
Several other Conservative politicians, many of whom were at the same meeting, are also now isolating.