Adar Poonawalla, the CEO of Serum Institute of India, talked to NDTV in an exclusive interview and answered a bunch of questions on an anti-Covid vaccine candidate. He said the efficacy of the vaccine will only be fully known after one or two years of use. "The indicators are all positive, but we will need to wait a year or two to be certain that the vaccine candidate will in fact have a long-term effect," he said.