The head of the World Health Organization (WHO), Tedros Adhanom Ghebreyesus, has said more than 200 million doses of AstraZeneca vaccine are expected to be sent to 142 countries by the end of May.

They will be delivered under the Covax scheme which provides poorer countries with free inoculations.

A shipment of nearly four million coronavirus vaccines has arrived in Nigeria - the third West African country to receive Covax shots after Ghana and Ivory Coast where vaccination campaigns have now begun.

Dr Tedros said vaccine deliveries were also planned on Tuesday to Angola, Cambodia and the Democratic Republic of Congo.