Serum Institute of India chief executive officer Adar Poonawalla on Sunday said its Covovax vaccine will get approval as a booster in the next 10 to 15 days, adding it works very well against the Omicron variant of coronavirus.Speaking to reporters on the sidelines of an event at Bharti Vidyapeeth University, Poonawalla, when asked about states and districts not getting Covishield vaccines, said there are ample stocks with the Union government for supply.