Minutes after registration for coronavirus vaccination opened up for all adults in India at 4 pm on Wednesday, the government’s CoWin portal and the Aarogya Setu app crashed for users across the country. Many complained that the site was not responsive, while others said they were not receiving a one-time password to finish the verification process.

At 4.35 pm, Aarogya Setu, the central government’s contact-tracing app to contain coronavirus, said the CoWin portal was working. “There was a minor glitch at 4 pm that was fixed,” it tweeted. “Eighteen plus can register.”

But social media users flagged that the website and app were still not responsive. Others said that despite completing the registration, they were unable to book a slot for vaccination.

Also read: Coronavirus vaccine registration for 18-45 age group opens at 4 pm. Here’s what you need to know

RS Sharma, Chief Executive Officer of National Health Authority, told ANI that the system will be able to function with the massive load of users. “On many days, we have had around 5 million people registering in a day,” he added. “We expect more than double that number today.”

Sharma said some state governments and hospitals may come on board for the vaccination drive after May 1, when the third phase of vaccination begins. “Therefore, the visibility into the bookings/vacancy available for vaccination will be available when states, hospitals come on board,” he added.

The Centre has made it mandatory for those between 18 and 45 years to register themselves on the CoWin portal or the Aarogya Setu app for vaccination. It has said that there will be no facility for walk-in registrations for beneficiaries in this age group.

Last week, the Narendra Modi government announced a number of changes to India’s coronavirus vaccination drive, including making every adult eligible to get a shot starting May 1. At present, only those over 45 and frontline workers are being vaccinated against the disease. Under the new rules, the Centre will automatically receive only 50% of vaccines produced by manufacturers. It will allocate these to the states under a new set of criteria, including the number of active cases of the infection, wastage of vaccines among others. The remaining 50% can be acquired by the states directly or by private hospitals and industrial establishments, at a price.

Biotechnology company Bharat Biotech’s Covaxin vaccine will cost Rs 600 per dose for state governments and Rs 1,200 for private companies. Meanwhile, Serum Institute’s Covishield price was reduced to Rs 300 from Rs 400 soon after the registration process was opened for all adults. It will sold to private hospitals for Rs 600.

At least seven states – Rajasthan, Andhra Pradesh, Chhattisgarh, Haryana, Maharashtra, Odisha and Telangana – have reported shortage of vaccines. The burden is likely to increase with around 60 crore more citizens in the 18 to 45 age group becoming eligible for the shots in the third phase.

The governments of Assam, Maharashtra, Rajasthan, Punjab, Chhattisgarh and Jharkhand have already announced that they were unlikely to begin vaccinating all adults from May 1 because of the unavailability of vaccines. Some of these states have alleged that the Centre had hijacked most of the stocks from manufacturers, leaving very little for them.

The problem is compounded by a massive surge in coronavirus cases in India. The second wave has led to at least 3,00,000 people testing positive for the infection in the past week, overwhelming hospitals and crematoriums. Many countries have offered to help India as social media is awash with frantic pleas for help, with people desperately seeking help to find oxygen cylinders, crucial medicines and beds in the Intensive Care Unit.

In the past 24 hours, India recorded 3,60,960 new cases, the largest single-day total in the world, taking the country’s total since the pandemic broke out in January 2020 to 1,79,97,267. A further 3,292 deaths, the highest so far, took the toll to 2,01,187.