The Covid-19 vaccine developed by Janssen is 66% effective, the Belgian company has announced.
The international trial looked at giving just one dose of the vaccine, which makes it significantly easier to roll out than those requiring two.
The UK has already pre-ordered 30m doses.
The news comes shortly after Novavax announced their jab was 89% effective. Both will need to be reviewed by regulators before they can be used.
Janssen, a pharmaceutical company owned by Johnson & Johnson, is also investigating whether giving two doses will give either stronger or longer-lasting protection.
The company said its initial findings showed one dose prevented 85% of severe cases.
Dr Paul Stoffels, the chief scientific officer at Johnson & Johnson, said that would “potentially protect hundreds of millions of people from serious and fatal outcomes of
The Janssen vaccine uses a common cold virus that has been engineered to make it harmless.
It then safely carries part of the coronavirus’s genetic code into the body. This is enough for the body to recognise the threat and then learn to fight coronavirus.
This trains the body’s immune system to fight coronavirus when it encounters the virus for real.
This is similar to the approach used by the University of Oxford and AstraZeneca.
BBCFollow us on social media