India administered more than a billion Covid-19 jabs since it started its vaccination drive in January this year.
It has fully vaccinated about 30% of the eligible population and 707 million have had the first dose.
India aims to fully vaccinate about a billion people by the end of 2021 but experts say the drive needs to pick up pace further to meet the target.
This milestone makes India the second country to reach the one billion mark after China who crossed this in June.
Reaching the one billion mark in 278 days means that India, on an average, administered 3.6 million doses per day. However, the number of doses actually administered each day since January was not consistent, and varied widely.
Logistical problems and supply bottlenecks, vaccine hesitancy and a debilitating second wave of Covid-19 during this period made the rollout harder.
India is still around 900 million jabs away from a fully vaccinated adult population, with little less than two-and-a-half-months to spare on the target.
Much will depend on levels of vaccine hesitancy and the availability of doses in the coming months.
From a sluggish start, India massively ramped up its vaccination drive, with more than 61,000 public and private health facilities offering the jab.
So far, the country has reported more than 34 million Covid cases, second only to the US, and more than 452,000 deaths behind the US and Brazil.