India has approved the COVID-19 vaccine developed by AstraZeneca and Oxford University, paving the way for a huge immunization campaign in the world’s second-most populous country.

Information and Broadcasting Minister Prakash Javadekar told reporters on Saturday the vaccine had been given the green light on Friday, confirming what sources close to the matter had told Reuters.

It is the first COVID-19 vaccine to be approved for emergency use by India, which has the highest number of infections after the United States and comes on the day the country is running a nationwide mock drill for vaccine delivery.

Javadekar said at least three more vaccines were waiting to be approved - local company Bharat Biotch’s COVAXIN, Zydus Cadila’s ZyCoV-D, and Russia’s Sputnik-V.

“India is perhaps the only country where at least four vaccines are getting ready,” he said.

“One was approved yesterday for emergency use, Serum’s COVISHIELD.,” he said, referring to the fact that the AstraZeneca/Oxford shot is being made locally by the Serum Institute of India (SII).

India’s Central Drugs Standard Control Organization (CDSCO) is expected to announce the dosage and other details about the shot later. SII had applied for a two full-dose regime about 28 days apart.

The AstraZeneca/Oxford vaccine, which was granted its first approval by Britain on Tuesday, is cheaper and easier to use than some rival shots - major advantages in tackling a pandemic that has claimed more than 1.8 million lives worldwide.

However, it has been plagued with uncertainty about its most effective dosage ever since data published in November showed a half-dose followed by a full dose had a 90% success rate while two full shots were 62% effective.

India’s regulator has also received an emergency-use application for the COVID-19 vaccine made by Pfizer Inc with Germany’s BioNTech - the first shot to secure regulatory approval in the West.

India has reported more than 10 million COVID-19 cases, though its rate of infection has come down significantly from a mid-September peak.

The country hopes to inoculate 300 million of its 1.35 billion people in the first six to eight months of this year.

SII, the world’s biggest producer of vaccines, has already stockpiled about 50 million doses of the AstraZeneca/Oxford shot, which will be sold to the government at about 250 rupees ($3.42) per dose and 1,000 rupees on the private market.