Zydus Cadila initiated enrolling and dosing participants for its phase 3 trial to determine the efficacy of its covid-19 shot ZyCov-D.“We started enrolment and dosing of participants from Saturday. The enrolment and dosing happen between 9 am and 5 pm," the principal investigator said. Unlike Bharat Biotech’s Covaxin and Covishield which are two-dose vaccines, ZyCov-D requires three shots.