Government officials have said they are eagerly waiting for Cadila to seek approval for ZyCoV-D soon, as a record rise in coronavirus infections have led to a public health disaster in the world's most populous country after China.

"We have just started producing doses," Sharvil Patel said in a Microsoft Teams interview on Friday. "But it is not meaningfully large."

He said the aim was to produce 10 million doses a month starting June, taking the in-house annual capacity to 120 million. The rest of the production, as required, will mainly come from third-party producers.

"We are already talking with two other manufacturers. We will slowly add more manufacturers," Patel said.

Its DNA plasmid product - which involves the injection of a small part of the virus's genetic code (DNA or RNA) to stimulate immune response in the recipient - is currently meant to be given in three doses but the company is also doing trials on a two-dose regimen, he said.

ZyCoV-D's success is crucial for India, the country with the world's biggest vaccine making capacity.

It exported more than 66 million vaccines before supplies ran tight for its own people as demand surged. The immunisation drive will expand from May 1 though domestic vaccine output will not increase for more than a month.

India is currently using the AstraZeneca shot and homegrown Covaxin. It has also approved Russia's Sputnik V and has urged Pfizer, Moderna and Johnson and Johnson to provide it with vaccines. All those shots will be imported, at least initially.

Patel said unlike some other drugmakers hit by U.S. curbs on exports of vaccine raw material, Cadila was sourcing its ingredients domestically.

"We did anticipate those challenges," he said. "Everything for us is done in India. Our supply chain is secure. We don't have any issues for the next 14-15 months."

(Writing by Krishna N. Das; Editing by Catherine Evans and Elaine Hardcastle)

By Sumit Khanna