Indian airlines started delivering batches of Covid-19 vaccines nationwide yesterday, preparing for the launch of a campaign to offer shots to 1.3 billion people, in what officials call the world's biggest vaccination drive.

Vaccinations are set to begin on Saturday in an effort that authorities hope will see 300 million high-risk people inoculated over the next six to eight months.

First to get the vaccine will be 30 million health and other frontline workers, followed by about 270 million older than 50 or deemed high-risk.

The first batches of Covishield, the Serum Institute of India's coronavirus vaccine, left Pune early yesterday morning for Delhi and 12 other cities.

Amid tight security, three temperature-controlled trucks rolled out of the Serum Institute gates with their precious cargo shortly before 5:00 am. The trucks carried 478 boxes of the vaccines, each box weighing 32 kg, news agency PTI reported quoting an unnamed official.

"Ready get set go! Stand by India! The vaccine to kill the disease is being loaded into the aircraft for distribution all over the country now," Pune airport tweeted.

"Civil aviation sector launches yet another momentous mission," tweeted Aviation Minister Hardeep Singh Puri as the first two flights operated by SpiceJet and GoAir took off with the vaccines to Delhi and Chennai.

"Today, Air India, SpiceJet and IndiGo Airlines will operate nine flights from Pune with 56.5 lakh doses to Delhi, Chennai, Kolkata, Guwahati, Shillong, Ahmedabad, Hyderabad, Vijayawada, Bhubaneswar, Patna, Bengaluru, Lucknow and Chandigarh," he said in another tweet.

Officials in Prime Minister Narendra Modi's western home state of Gujarat said vaccine distribution was their top priority.

"These vaccines will be taken to the cold storage from the airport and swiftly delivered to vaccination booths," said Nitin Patel, the state's deputy chief minister.

Modi's government signed purchase pacts on Monday with vaccine maker Serum Institute of India (SII) more than a week after approving the vaccine developed by Britain's AstraZeneca and Oxford University.

"We've given a special price of 200 rupees ($2.73) for the first 100 million doses only to the government of India on their request," Adar Poonawalla, the firm's chief executive, told Reuters television's India partner ANI.

The price represented a gesture of support for the common man, those who are poor and vulnerable, and healthcare workers, he said, adding, "After that we'll be selling it at 1,000 Indian rupees in private markets."

Meanwhile, Foreign Minister Subrahmanyam Jaishankar said yesterday India will be able to decide on exports of coronavirus vaccines within the next few weeks, as governments abroad seek to shore up supplies.

Jaishankar told the Reuters Next conference that India understood the anxieties of foreign governments about getting the vaccines delivered to their populations.

"We will get clarity pretty soon on what our own consumption is going got be, (what) deployments are going to be. And we will keep our global role very much," he said.

Last week, Brazilian President Jair Bolsonaro wrote a letter to Modi asking to expedite a shipment of AstraZeneca's vaccine, which is being made by Serum Institute of India. 

Bangladesh this week said it expected to receive initial shipments of the vaccine from SII by January 25.

"The policy of course is we will start the rollout in India. We have our own challenges," Jaishankar said.

"A number of countries are in touch with us... and what we are telling them is, look, this is the first month," he added. "The production is now coming into stream. There is a certain amount of stock taking going on."

Health authorities in eastern and western Indian states said they would make use of experience gained from running regular child immunisation programmes for polio to ensure full coverage in what they called the world's biggest vaccination drive.

But creaking transport networks and a crumbling healthcare system add an enormous layer of complexity, they said.

India's tally of close to 10.5 million infections is the world's second highest after the United States, although the rate of increase has been slowing.