The South Asian nation of 1.3 billion people is recovering from a devastating second wave of the coronavirus this year that killed about 250,000 people and infected tens of millions.
About 75 per cent of the approximately 950 million adults eligible for vaccination have received at least one dose of the vaccine and one third both doses since the inoculation drive was launched on January 16.
“India scripts history,” Prime Minister Narendra Modi wrote on Twitter before addressing the nation to mark the billion vaccinations milestone.
“Congrats India on crossing 100 crore vaccinations. Gratitude to our doctors, nurses and all those who worked to achieve this feat,” he said.
Mr Modi also visited a Delhi hospital to show support for health workers who have been at the forefront of the fight against the pandemic.
The health ministry released a song dedicated to the vaccination drive, and authorities planned to light up historic monuments and hoist a handmade national flag at the Red Fort in the capital.
India wants to inoculate the entire adult population by the end of the year despite initial hiccups in the campaign because of widespread vaccine shortages that forced the world’s largest vaccine-producing nation to ban all exports.
Despite administering between five million and eight million vaccinations a day, experts say the slow uptake among people due for their second dose is worrying.
India began its inoculation drive with two vaccines – the Oxford-AstraZeneca vaccine, produced by Serum Institute of India under the name Covishield, and the homegrown Covaxin developed by Bharat Biotech. Four other vaccine candidates have received emergency approval since, but almost 90 per cent of the doses administered are Covishield.
It also plans to start vaccinating children between 12 and 17 years of age with ZyCoV-D, another homegrown vaccine that was approved by the country’s drug regulator in August.
Mr Modi’s government faced criticism for its vaccine procurement policy that divided quotas between states and the federal government, leading to widespread shortages and derailing the vaccination campaign for weeks. The government scrapped the policy after scathing comments from the Supreme Court and began working to secure hundreds of millions of doses.
In recent months, India has maintained a stock of 100 million doses while lifting its export ban.
About 18,000 new daily infections were confirmed on Thursday, down from 415,000 in May. Daily deaths have fallen to an average of 200 from 4,000 at the peak of the second wave.
Experts say that while one billion vaccinations is cause for celebration, there are many challenges that the country needs to focus on.
“This is a commendable feat by any yardstick,” said Dr Chandrakant Lahariya, a physician and vaccinologist in New Delhi, who praised the “frontline workers who have made this possible”.
“But the battle is half won. One hundred crore doses essentially make around 55 per cent of the targeted 1.88 billion shots that need to be administered to the adult population,” he told The National.
“A quarter of India’s adult population still needs to receive the first shot. Vaccine hesitancy, access and the challenge of delivering [the] first shot – and second shot to the ones who have received first shot – are other aspects and need to be focused on.”