Pfizer starts investigation of oral drug for counteraction of COVID-19 Kumar Jeetendra | September 27, 2021 Pfizer Inc said on Monday it has started a mid-to-late-stage study testing its investigational oral antiviral drug for the prevention of COVID-19 infection among those who have been exposed to the virus. The company and its rivals, including U.S.-based Merck & Co Inc and Swiss pharmaceutical Roche Holding AG, have been racing to develop the …