India has ordered 10 million more doses of the AstraZeneca Covid-19 vaccine from the Serum Institute of India (SII) and 4.5m more of a homegrown one from Bharat Biotech, company representatives told Reuters.

Just the two shots have been used in what India calls the world's biggest immunisation programme to cover 300m people by August, starting with healthcare and other workers to reach the elderly and those with existing conditions by March.

SII, the world's biggest vaccine maker, had supplied 11m doses for the inoculation campaign, which has covered 6.3m front-line workers since it began on Jan 16.

“The second order is already in place, it's for 10 million doses,” an SII spokesman said, adding that the figure was part of the 100m doses the company has agreed to sell to the government for Rs200 ($2.74) each.