India on Monday administered a record over eight million Covid-19 vaccine doses, more than double the average in June so far, as the inoculation campaign shifted into new rules under which all adults may walk in for free vaccinations at all government sites.

The Union health ministry’s digital platform that tracks the campaign in real-time had logged by 10.30pm a total of 8,407,420 doses, a sharp rise over the average 3.1 million daily inoculations from June 1 to 20, surprising sections of experts hitherto concerned about the campaign’s slow pace.

The experts said India would be able to fully vaccinate nearly its entire estimated eligible population of over 950 million people if the pace of inoculations on Monday is sustained throughout the rest of the year and backed by steady vaccine supplies.

“This is a big jump. I don’t think anybody expected this. It’ll be excellent if they can maintain this through supplies,” said R. Ramakumar, a health economist and professor of developmental studies at the Tata Institute of Social Sciences, Mumbai.

Prime Minister Narendra Modi described the record-breaking rise in vaccinations as “gladdening.”

“The vaccine remains our strongest weapon to fight Covid-19,” Modi wrote on Twitter. “Congratulations to those who got vaccinated and kudos to all frontline warriors working hard to ensure so many citizens got the vaccine. Well done India!”

Health officials have attributed multiple reasons for the rise, including the new rules that allowed for the first time anyone to walk into any vaccination centre and seek on-site registration, a feature hitherto available only for those 45 years or older.

“The walk-in registration is only one factor — I think we’re seeing the accumulated effects of many things,” said Samiran Panda, the chief of the epidemiology division at the Indian Council of Medical Research, who is among the technical experts guiding the government’s vaccination policy.

“Vaccine supplies are increasing. We’ve taken painstaking efforts at communicating the need for vaccines to people across the country. We’ve urged districts to prioritise the vulnerable groups and vaccinate them as quickly as possible,” Panda said.

Another health official said about 67,000 vaccination centres across the country were active on Monday with more than half of them in rural areas.

“The walk-in feature would have made a big difference in rural areas,” said Narendra Arora, another senior adviser who has guided the Covid-19 vaccination policy. “But we have been preparing for this day through micro-planning and strong supply-chain management, and mobilising groups of 100 to 120 people in rural areas to visit vaccination centres.”

Arora said the country has the capacity to increase the number of sites to 75,000. “Our target is to reach 10 million doses per day,” he told The Telegraph.

The vaccination rules changed on Monday with the Centre now supplying doses to all states to vaccinate all adults 18 years or older for free in government centres, allowing people to opt for paid vaccinations in private hospitals.

Health officials have said, under these rules, doses to private hospitals would also be channelled through state governments to ensure that they are evenly distributed and not overwhelmingly used up by a few networks of large hospitals.

The campaign launched on January 16 has administered over 283 million doses, but only about five per cent of the eligible population is fully vaccinated with the required two doses, the pace of inoculations primarily constrained by slow vaccine supplies.

Health experts have estimated India would need to administer an average 8.8 million doses daily to complete the estimated 1.9 billion doses during the remaining 183 days of the year to achieve its target of vaccinating all.