Single dose vaccines could be just weeks away for Britain as the regulation process is set to begin this week.
The Johnson & Johnson vaccine, which has now been approved for use in the US, could start the UK's formal regulatory approval process in the coming days.
The UK has ordered 30 million doses of the jab while the US has ordered 100 million and Canada 38 million.
The Medicines and Healthcare products Regulatory Agency, which must carry out the checks for the UK, did not respond to a request for a comment.
Health sources said that the jab was not yet being considered by the MHRA for formal approval, a process which normally takes two weeks based on the timelines for the Pfizer and AstraZeneca vaccines.
A senior government source said the MHRA formal process was “very likely” to start this week.
The Department of Health and Social Care declined to comment.
A department source told the Sunday Telegraph: “We are working with them to complete the rolling review process and we look forward to receiving more data from them as soon as possible.”
A US panel on Friday recommended the one-dose Covid-19 shot – developed by Johnson & Johnson’s vaccines division Janssen – for emergency approval.
And that has now been rubber-stamped by the US Food and Drug Administration (FDA).
The vaccine is set to be a cost-effective alternative to the Pfizer and Moderna vaccines, and can be stored in a refrigerator instead of a freezer.
Trials found it prevented serious illness but was 66% effective overall when moderate cases were included.
In the UK, it could help keep the pace of the vaccine rollout high as younger people start receiving their first dose as increasing numbers of older people get their second.
The vaccine is made by the Belgian firm Janssen.
President Joe Biden hailed it as "exciting news for all Americans, and an encouraging development", but warned that 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."
