India has administered one billion doses of Covid-19 vaccines.

About 75% of India’s total eligible adult population has received at least one dose, while around 30% is fully immunised, officials said.

The country of nearly 1.4 billion people is the second to exceed a billion cumulative doses after China, the most populous country, did so in June.

Coronavirus cases have fallen sharply in India since the devastating months at the start of the year when the highly transmissible Delta variant, first detected in the country a year ago, was infecting hundreds of thousands daily.

People get inoculated against coronavirus in Hyderabad, India
People get inoculated against coronavirus in Hyderabad, India (AP)

On Thursday, India confirmed more than 18,400 new cases. Active cases make up less than 1% of its total caseload, now more than 34 million, including more than 450,000 deaths, according to the health ministry.

Officials have bolstered the vaccination campaign in recent months, which experts say has helped control the outbreak. The country began its drive in January.

Still, there remains a worrying gap between those who have received just one shot and those fully immunised.

Ramping up the second dose is “an important priority,” said VK Paul, the head of the country’s Covid-19 taskforce.

“We would like to see this number go up. Complete coverage is absolutely critical,” he said.

India earlier said it aimed to vaccinate all eligible adults by the end of the year, but experts say the current pace of immunisation will need to increase to meet this goal.

Health workers celebrate India administering one billion doses of Covid-19 vaccines
Health workers celebrate India administering one billion doses of Covid-19 vaccines (Rajanish Kakade/AP)

Billboards announcing the achievement with a photo of Prime Minister Narendra Modi were posted across New Delhi. Outside a local politician’s house in the city, residents gathered as sweets were distributed.

Officials said they will mark the milestone at vaccination centres and hospitals where frontline workers will be celebrated.

India, an important supplier of vaccines globally, halted exports in April as cases at home surged and only resumed exports earlier this month. The government is now optimistic that the country’s rising vaccine supply will be enough to cover its international and domestic commitments.

Both of the two main suppliers have ramped up production, with the Serum Institute now producing around 220 million doses a month and Bharat Biotech about 30 million, Mr Paul said.

Serological surveys done in June and July showed that more than 60% of the population had antibodies to coronavirus, reducing the likelihood of another massive surge in coming months, according to some experts.

Members of India’s ruling party distribute sweets
Members of India’s ruling party distribute sweets to celebrate one billion doses of the vaccine being administered (Altaf Qadri/AP)

Even states where infections were swelling a few weeks ago, such as Kerala, have seen a sustained decline.

“There is a sense of comfort that India has suffered the worst of the Delta variant, but this must be accompanied with a feeling of caution,” said K Srinath Reddy, president of the Public Health Foundation of India.

“Even if cases go up, we are unlikely to see the scale of the surge earlier – if that does happen, it would be fairly unexpected.”

In recent months, life in India has swung back to normal. Markets are buzzing with activity, tourists can enter the country after a 19-month hiatus and it is gearing up to celebrate Diwali, the Hindu festival of lights.