Serum Institute of India, the world's largest vaccine maker by number of doses produced, has sought government approval for emergency use authorisation of the coronavirus vaccine that it is developing with the University of Oxford and British drugmaker AstraZeneca, sources have said. The Pune-based pharma firm is the second to do so, say sources, after American firm Pfizer sought approval from the drug regulator - the DCGI (Drugs Controller General of India)- for its COVID-19 vaccine, cleared by