The Indian government has ordered 660 million vaccine doses for August to December, its largest procurement, local news reports say, as state authorities and health experts warn that shortages could leave millions vulnerable if coronavirus infections surge again.

The federal government aims to inoculate all of the country's estimated 944 million adults by December, a target health experts have said is ambitious, as only eight per cent of that number is currently vaccinated with the mandatory two doses.

Several states have reported vaccine shortages, with many inoculation centres shut and people having to wait for long hours at others for their shot.

The government has now ordered 375m more doses of AstraZeneca's locally produced Covishield and 285m doses of Bharat Biotech's homegrown Covaxin, the Economic Times newspaper has reported, citing sources.

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