Nearly 80 lakh people registered for Covid-19 vaccination on the government's CoWIN portal on Wednesday, as the Centre opened up the process for the upcoming mass vaccination drive, where everyone above 18 years of age can get inoculated, a government official said.

National Health Authority CEO RS Sharma in a tweet said there have been 79,65,720 registrations on Co-WIN on the day.

“There have been 79,65,720 registrations on Co-WIN today, most of these in the last three hours (16:00-19:00) and mostly of 18-44 age group. We have seen a traffic of 55,000 hits per second. System functioning as expected,” he wrote.

A tweet from the handle of the Aarogya Setu app said more than 35 lakh people had registered in the first hour.

“More than 35 lakhs people registered in the first hour after launch of 18 plus registration on http://cowin.gov.in. Appointments for 18-44 will be available when State Govts and Private Vaccination Centers schedule sessions.”

However, as registration opened up, many people took to social media to complain about the technical problems they faced trying to register themselves for the third phase of the inoculation drive that is scheduled to begin from May 1.

Some of them complained that the portal was not responding while others complained that it had crashed.

At 4.35 pm, a tweet from Aarogya Setu said the CoWIN portal is working and that there was a minor glitch at 4 pm, which was fixed.

"Cowin portal is working. There was a minor glitch at 4 pm that was fixed. 18 plus can register," it said.

At 4.54 pm, a tweet from the same handle stated: "Vaccination appointments for 18 plus will be possible once the state governments and private vaccination centres schedule vaccination sessions. Registration is happening on cowin.gov.in."

Registration for the newly-eligible category for Covid-19 vaccination is possible through the CoWIN platform and the Aarogya Setu app.

After registration, taking an appointment to get a Covid-19 vaccine jab would be mandatory for those aged between 18 and 44 years as walk-ins will not be allowed initially, officials had said.

Those above 45 years of age can still avail the facility of on-site registration to get vaccinated, they had said.

As India witnesses a surge in coronavirus cases, it has decided to allow all citizens above 18 years of age to get vaccinated from May 1.

"An increased demand is expected once the vaccination is opened for all. For the purpose of crowd control, registering on the CoWIN portal and making an appointment to get a vaccine will be mandatory for those aged between 18 and 45 years. Walks-in will not be allowed in the beginning so that there is no chaos," an official had said.

The inoculation process and the documents to be provided to get the jab remain the same.

"Registration of citizens in the 18-44 age group will start with only online registration on CoWIN from April 28 onwards," the health ministry had said.

Also, from May 1, the types of anti-coronavirus vaccines and their prices will be displayed on the CoWIN portal for the citizens to make an informed choice at the time of booking an appointment at a private vaccination centre.

While those aged 18 to 44 years will be eligible to receive vaccination on payment from any of the private Covid vaccination centres (CVCs), they shall also be eligible to receive a jab from a government CVC in a state or a Union Territory that decides to lower the minimum cut-off age for eligibility.

As provided in the Liberalised Pricing and Accelerated National Covid-19 Vaccination Strategy document, all priority groups such as healthcare workers, frontline workers and citizens aged 45 years and above shall continue to be eligible for vaccination for free from government CVCs and on payment from private CVCS.