India signed its first order for an unapproved Covid-19 vaccine on Thursday, a day after criticism from the Supreme Court over its bungled vaccine rollout that has left millions of people vulnerable after almost 338,000 deaths.

So far, only 4.7% of the 950 million adult population have been given two vaccine doses. The world's second most populous country is reeling from a widespread second wave of infections that killed around 170,000 people in April and May alone.

The government will buy 300 million vaccine doses from local firm Biological-E and has put down an advance of $205.6 million, the health ministry said, even though the vaccine is still going through Phase III clinical trials.