Johnson and Johnson says its vaccine is 66% effective at preventing moderate to severe Covid

The company has released the results of its trials

The trials show the jab is 85 percent effective in preventing severe disease but is less effective in South Africa, where a new variant of the virus has emerged.  

The difference between this and other vaccinations is that it’s delivered in just one jab - not two.

Sky's science correspondent Thomas Moore explains why that's significant:

"Because it can be rolled out so much more quickly, that you could extend this far into low and middle income countries very rapidly they have hardly had any doses of the vaccine so far and it's at low cost"