India administered its one billionth Covid-19 vaccine dose on Thursday as it fights its way back from a devastating surge in cases that brought the health system close to collapse.
Prime Minister Narendra Modi hailed the feat as a "triumph of Indian science", but authorities remain on guard for a new pandemic wave.
About three-quarters of adults in the country of 1.3 billion people have had one shot and 30 percent are fully vaccinated, according to government figures.
But hundreds of millions of Indians under 18 -- who make up about 40 percent of the population -- have not had a single shot.
More than 200,000 people died in a devastating Covid wave from mid-April to mid-June. Hundreds of thousands of people were stricken with the Delta variant and many hospitals and crematoriums were overwhelmed.
Cases have since fallen sharply since. Fewer than 20,000 infections are reported each day and much social activity has resumed.
Mumbai, one of the worst-hit cities, recently reported zero Covid deaths in a day for the first time since the pandemic began.
In celebration of the vaccine landmark, Modi paid tribute to India's health workers and monuments in the capital New Delhi were to be lit up in the national colours.
Neighbouring Bhutan and Sri Lanka hailed the milestone, and the United Nations Children's Fund representative in India, Yasmin Ali Haque, said it was a "tremendous achievement".
"As Indian families recover from the recent devastating Covid-19 wave, for many this milestone means hope."
Only China's government, which says it has given out more than 2.3 billion shots, has administered more doses than India.
The billion jabs were administered in 279 days despite shortages, which forced the world's biggest vaccine producer to halt exports for several months.
"During the first wave, I remember hearing people talking about whether coronavirus was real or not," said Reham Ali, a 49-year-old taxi driver in New Delhi who has had one shot.
"Now, people know that it is and there is less hesitancy. The second wave was an eye-opener."
Vaccine exports have tentatively resumed, with officials saying the "pharmacy of the world" will be back in full swing in 2022.
Most restrictions on social activity have been lifted and huge crowds packed markets and malls during India's main religious festival season -- a boost to the battered economy.
This has sparked fears of another Covid wave and a renewed government push to encourage vaccinations and stockpile oxygen stores.
"I think it is unlikely that we will see a third wave that in any way resembles the second wave," said Gangandeep Kang from the Christian Medical College, Vellore.
"The only situation where that can happen is if we have a completely new virus variant. Then it'll be a new pandemic," she told AFP.
India has the world's second-highest number of cases: 34 million.
Its 452,000 Covid deaths are the third-highest, behind the tolls in the United States and Brazil.
But under-reporting is widespread and some studies have estimated India's true toll could be up to ten times higher.
By: Aishwarya Kumar / AFP