Covid Vaccine: Single-dose Johnson & Johnson jab is 66
A single-dose coronavirus vaccine developed by Janssen is 66% effective, the Belgian company has announced.
Crucially, no one needed hospital treatment or died from Covid after the jab took effect in the international trial.
Health secretary Matt Hancock said if the jab was approved by the UK's regulator it could "significantly bolster" the vaccine programme.
The UK has ordered 30 million doses of Johnson & Johnson's Janssen jab.
Prime Minister Boris Johnson said that the results from the early trials were "very encouraging" and if approved - by the Medicines and Healthcare Products Regulatory Agency (MHRA) - doses of the jab should be available later this year.
The trial looked at giving just one dose of the vaccine, which makes it significantly easier to roll out than those requiring two.
Although there are also signs the jab is less effective against the new variant that is spreading in South Africa.
The news comes shortly after Novavax announced their jab was 89% effective overall in the UK and 60% in South Africa. Both new vaccines will need to be reviewed by regulators before they can be used.
Janssen - which is owned by the pharmaceutical firm Johnson & Johnson - is also investigating whether giving two doses will give either stronger or longer-lasting protection.
The fact it works as a single dose and can be kept in a standard fridge, while others need super-cold storage, means the vaccine could have a significant role around the world.
"A one-shot vaccine is considered by the World Health Organization to be the best option in pandemic settings," said Dr. Paul Stoffels, the chief scientific officer at Johnson & Johnson.
He added the vaccine could "potentially protect hundreds of millions of people from serious and fatal outcomes of Covid-19".
The company is aiming to make one billion doses this year.