"I wish other companies also had taken that risk, because the world would have had many more doses."
Mr Poonawalla criticised the patchwork of global regulatory systems and lack of harmonisation for production delays.
He said the major regulators, including the UK's Medicines and Healthcare products Regulatory Agency (MHRA), the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA), could have united and agreed a quality standard.
He also criticised national governments, claiming that regulators in the countries that are making the vaccines, from India to Europe, could have united to agree a standard international benchmark.
"Why can't we still harmonise it and save all this time, especially even for the new vaccines. I'd hate to have to go through all this again."
Mr Poonawalla played down concerns about new variants: "Anyone who has taken that [Oxford AstraZeneca] vaccine so far hasn't had to go to hospital or go on a ventilator and had their life at risk.
"They've also passed that disease on to others. So yes, it's not an ideal situation, but it has protected your life."
In India, SII is also involved the world's largest inoculation programme, to vaccinate 300 million by August. But, according to Bloomberg, only 56% of people eligible to get a shot have actually stepped forward.
"A lot of vaccine hesitancy traditionally has come about when either celebrities or non-experts have said vaccines are not safe," said Mr Poonawalla.
"I always just request celebrities and others who have this tremendous power on the social networks, to just be a bit responsible and read up on the facts before they say anything."