Separately, a recent study by the Indian Council of Medical Research (ICMR) involving 98 people, 18 of whom had inadvertently received Covishield as the first dose and Covaxin as the second in Uttar Pradesh, showed that combining these two COVID-19 vaccines elicited better immunogenicity than two doses of the same vaccine.

The study also found that immunisation with combination of Covishield and Covaxin was safe and the adverse effects were also found to be similar when compared to the same dose regimen.

Kerala accounted for more than half of the COVID-19 cases recorded in the country in the last seven days, the Centre said on Tuesday.