Significant adverse effects are \"unlikely\" if an individual's second Covid-19 vaccine dose is different from the first, the centre said on May 27 afternoon. \"This should be looked into,” Dr VK Paul, the Chair of NEGVAC (National Expert Group on Vaccine Administration for COVID-19), said. Earlier this month 20 UP villagers were given Bharat Biotech's Covaxin when they went for the mandatory second dose. They were administered Covishield on their first visit in early April. Days before the UP mix-up a 72-year-old Maharashtra man was also given mixed doses. The effectiveness, or impact, of mixing vaccines is still a subject of global research. India has administered over 20 crore vaccine doses so far.