Serum Institute of India (SII) chairman Dr Cyrus Poonawalla today said he is not in favour of administering two different coronavirus vaccines for better efficacy. Mr Poonawalla, whose firm makes the Covishield vaccine, was speaking to reporters after receiving the Lokmanya Tilak National Award in Pune. "I am against the mixing of two different vaccines. There is no need to mix two different vaccines," he said, when asked about a recent ICMR study that a cocktail of Covishield and Covaxin could generate better immunity.