The Moderna vaccine has become the third coronavirus jab to be approved for use in the UK.
The US-based company's vaccine was shown to have 94% efficacy against COVID-19 in final trials.
Seven million doses have been ordered by the UK government with a further 10 million expected to follow - but it will likely not become available until March.
This is because it is being manufactured in the US at first, and will take a few months before manufacturing facilities in Europe will be ready to distribute.
American authorities have also approved the Moderna vaccine. The country's FDA based its decision on results from a late-stage study of 30,000 volunteers.Advertisement
The UK was the first country in the world to approve the Pfizer/BioNTech vaccine, and has since also begun rollout of the Oxford/AstraZeneca jab.
On Thursday, PM Boris Johnson said 1.26 million jabs had been given in England, 113,000 in Scotland, 49,000 in Wales, and 46,000 in Northern Ireland.
The government has set a target to deliver first doses to 15 million of the most vulnerable by 15 February.
The Moderna vaccine is much easier to distribute than the Pfizer jab, which must be stored at about -70C to maintain optimal efficacy.
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.