The desperate wait gets longer

India started its vaccine drive in January, amid plummeting cases and a fair bit of optimism. The country's very own Serum Institute of India (SII), the world's largest vaccine maker, was meant to supply most of the jabs as the country headed towards an ambitious target - covering 250 million people by July.

As part of a World Health Organization (WHO)-led scheme, India even exported vaccines to countries that needed them.

But three months on, Covid cases and deaths are spiking across the country. Only about 26 million people have been fully vaccinated out of a population of 1.4 billion, and about 124 million have received a single dose. Prime Minister Narendra Modi's government has cancelled exports, reneging on international commitments. Worse, vaccine stocks in the country have nearly dried up, and no-one is sure when more will arrive.

How did India get here?

Demand surged when supply was short

On Wednesday afternoon local time - just as millions of Indians were trying to register online for a Covid jab - the vaccine portal and its accompanying apps crashed.

Starting 1 May, India is opening up vaccination for roughly 600 million more people, to cover 18-44 year olds. But CoWin, as the platform is known, couldn't handle it.

"I am stuck in an OTP loop of horrors," said one 33-year-old while trying to register for her jab. OTPs, or one-time passwords sent to mobile numbers, are a favoured Indian way of verifying identity online. She had a string of messages with OTPs, but nowhere to put them.

Others didn't even get that far - #WaitingForOTP was soon trending on Twitter, and the memes and jokes followed. Eventually the site was back up - but, to the disappointment of more than 13 million people who did finally register, not a single vaccine centre had slots for booking.

These are just a fraction of the 600 million people newly eligible for a jab. There's also another 200 million or so, 45 and above, who are yet to get their second jab.

Experts say the government should have finished vaccinating people above 45 before opening it up further, especially when supply was low. In fact, this appeared to be the plan until as recently as 6 April, when the health ministry said the drive could not simply be "accelerated" and that it was not yet considering expanding it to all adults.

It's likely the rapid, unrelenting surge in cases and reports that younger people were increasingly being admitted to hospital with severe symptoms led to the decision.

"They should have held their nerve and focused on the vulnerable," says economist Partha Mukhopadhyay. "Now they [the 45 and above] have to compete with 600 million new demanders."

Since the announcement, those who have received no doses or a single dose so far have been queuing up at centres before supply runs out, raising the risk of infection. But that's not the only factor that has thrown India's vaccine drive into chaos.

'It's a seller's market'

Until now, India's federal government had been the sole purchaser of the two approved vaccines - Covishield, developed by AstraZeneca with Oxford University and manufactured by SII; and Covaxin, made by a local firm Bharat Biotech.

But it's now thrown open the market to not just 28 state governments, but also private hospitals, all of whom can directly negotiate and buy from the two vaccine makers. And they have to pay far more.

The federal government still gets 50% of stocks for 150 rupees ($2; £1.40) per dose, but states have to pay double that, and private hospitals eight times as much - all while competing for the remaining half.

The sudden transfer of responsibility - it was announced just 10 days ago - left officials with little time to negotiate prices or stockpile vaccines. Especially since vaccine makers still have orders pending from the federal government.

"We are the only country in the world that is allowing sub-national governments to directly buy from vaccine makers. This is not at all well though-out," says Mr Mukhopadhyay.

The different prices are concerning, says Srinath Reddy, a public health expert who advises federal and state governments on tackling Covid-19. "All vaccination should be free, it's for public good," he says. "And why should states pay a higher price? They are also using tax payer money."

He fears that it's now a "seller's market", where the poorest Indians are likely to be last in line.

Two private hospital chains have already announced that they will roll-out the vaccine for 18-44 years olds from tomorrow, but it's unclear how they managed to secure supply when states are struggling. Some have even said they are putting the expansion on hold until more vaccines arrive.