The Johnson & Johnson single-shot coronavirus jab has been given the green light by US regulators.
It is the third vaccine the US Food and Drug Administration has approved, after Pfizer and Moderna, but the first to require only one shot.
Trials found the Johnson & Johnson jab prevented serious illness but was 66 per cent effective when moderate cases were included.
While lower than two doses of Pfizer or Moderna, the trials were organised differently and took place when new variants were in circulation making comparison difficult.
Crucially there were no deaths among participants and no hospital admissions 28 days post-jab.
The company said it is ready to ship 4m doses immediately, slightly lower than the 10m the US government was hoping for. However Johnson & Johnson did say it had agreed to provide the US with 100m doses by the end of June.
The UK, EU and Canada have also ordered doses.
Over the weekend French industry minister Agnes Panier-Runacher said the European Medicines Agency was on the verge of approving the drug.
President Joe Biden said the “exciting news” was an “encouraging development” but warned “the fight is far from over.”
“Though we celebrate today’s news, I urge all Americans – keep washing your hands, stay socially distanced, and keep wearing masks,” he said in a statement.
“As I have said many times, things are still likely to get worse again as new variants spread, and the current improvement could reverse.”