The World Health Organization recommends using the vaccine developed by the University of Oxford and AstraZeneca.
Their experts said it should be used even in countries where variants of coronavirus that make the vaccine less effective are circulating.
The WHO also says the vaccine can be used in people aged over 65.
And that spacing out the two doses, as is happening in the UK, makes the vaccine more effective.
The WHO’s Strategic Advisory Group of Experts on Immunization, known as Sage, has been scrutinising evidence from vaccine trials.
Its interim recommendations
say the vaccine is 63% effective overall.
A variant in the country has acquired mutations that seem to help it evade immunity from vaccines or from previous infections.
However, Oxford scientists still expect their vaccine to prevent people from becoming seriously ill from Covid-19 and needing hospital treatment.
“There is no reason not to recommend its use even in countries that have circulation of the variant,” said Dr Alejandro Cravioto, the chairman of WHO’s Sage.