India will likely take at least three to four months to complete Covid-19 inoculation efforts for frontline workers and people above 60, or with underlying health conditions, the executive director of Serum Institute of India said Thursday.

In January, the South Asian country rolled out the world’s largest vaccination campaign for some 300 million people out of its massive 1.3 billion population. As of Wednesday evening, more than 36 million people have been inoculated per data from the Indian health ministry.

“The number of doses which are required in India are huge,” Suresh Jadhav told CNBC’s “Capital Connection,” adding that the vaccination program is a gigantic task that is impossible to rush to completion in a short period of time.

“At a speed of about 50 (million) to 60 million doses per month, this program will continue and they will cover this population of 300 million in another about three to four months time,” he said.

Jadhav participated this week in the Asian Development Bank’s Southeast Asia Development Symposium 2021.

The Pune, India-based Serum Institute has emerged as a crucial player in Covid vaccination efforts both in India and globally. It’s the world’s largest vaccine maker by volume and is manufacturing the Covid-19 vaccine developed by British-Swedish pharma giant AstraZeneca and Oxford University, which is known locally as Covishield.

It has supplied millions of doses to the Indian government as well as to Covax, a global vaccination initiative led by the World Health Organization and others to ensure equitable distribution of shots in less wealthy countries.

Responding to the growing demand for its Covid vaccine, Serum Institute CEO Adar Poonawalla last month asked foreign governments to be patient and said, without explaining further, the company had been told to meet domestic demand first.

Jadhav explained that Serum Institute is capable of fulfilling current orders that have been placed by the Indian government and said it has already supplied about 59 million doses to Covax. He added that Serum Institute is planning to expand its capacity by end April or early May, when it aims to increase production by another 40 million to 50 million doses.

At present, Serum Institute can reportedly produce more than 70 million doses a month.

Last week, the United States, Japan and Australia pledged to help Indian companies expand their Covid vaccine production capacities and provide more doses to the global supply pool.

India is also using a locally developed vaccine from Bharat Biotech that was created in collaboration with the state-run Indian Council of Medical Research.