Serum Institute of India CEO Adar Poonawalla on Wednesday said the company has restarted manufacturing of COVID-19 vaccine Covishield amid rising numbers of cases of the virus infection. He said the company already has six million booster doses of Covovax vaccine available and adults must take the booster shot. "Just as a precaution, at risk we have done it so that people have Covishield as a choice if they want it," Poonawalla told PTI on restarting manufacturing of the vaccine.