The first shipment of Covishield - the coronavirus vaccine developed by AstraZeneca and Oxford University and manufactured by the Serum Institute - is expected to land at Delhi's Indira Gandhi airport tonight.
The shipment, which is being carried on Air India flight AI 850 from Pune, will likely be immediately shifted to the Rajeev Gandhi Superspeciality Hospital, where a cold storage facility has been set up. The hospital will serve as the main storage facility for the national capital and from there vials will be sent to over 600 cold chain points in the city.
In the event it is not possible to transfer the shipment tonight, it may be kept at the airport (which also has a cold storage facility) and taken to the hospital early Friday morning.
"The airport has cold chambers which can store at least 27 lakh vials and up to 80 lakh vials can be transported per day," Videh Kumar Jaipuriya, the airport's CEO, told NDTV last month.
Delhi airport has two cold chambers in the main cold storage area - one can maintain temperatures at -20 degrees Celsius and will likely be used to store the Moderna vaccine, should it come to India.
The other - which can maintain a temperature range of two to eight degrees Celsius - has been earmarked to store Covishield and Covaxin, the vaccine from Bharat Biotech.
Mr Jaipuriya also said the airport has special temperature-controlled containers to transport the vaccine vials and dedicated "green channels" for passage of vaccine trucks for faster movement.
This morning Health Minister Dr Harsh Vardhan said the government was in the final stages of preparation for vaccine roll-out. In the first phase around 30 crore people - healthcare staff and frontline workers in the battle against the virus - will get the vaccine, he said.
The centre has already conducted one dry run to test for potential problems ahead of vaccine delivery, and a second has been scheduled for Friday. A date for the vaccination drive has yet to be announced, the Health Ministry has indicated that it could happen within the next couple of weeks.
Last week Serum Institute CEO Adar Poonawalla said a majority of the first 50 million doses had been reserved for India. He said: "...for the first month, most of our doses will go to India".
Mr Poonawalla had earlier told NDTV the government had agreed to buy 100 million (10 crore) doses at Rs 200 per dose. Sources said the final price was subject last-minute negotiations.
As well as Delhi, vaccine shipments will reach other major Indian cities over the next 72 hours.
Pune has been designated as the central hub for vaccine distribution in India.
Delhi and Karnal in Haryana have been chosen as mini-hubs for vaccine distribution in north India. In the east Kolkata and Guwahati will be the mini-hubs, with the latter also the nodal point for distribution in the northeast. Chennai and Hyderabad are designated storage points for southern states.
India has given emergency use approval to Covishield and Covaxin. A third vaccine - developed by Pfizer - is also being considered but has yet to get permission. The Pfizer vaccine has been cleared for use and rolled out in the United Kingdom, the United States and other countries.