In June, WHO had accepted Bharat Biotech's EOI i.e. Expression of Interest for its approval.
The trials will be conducted on 300 healthy volunteers.
Experts have speculated that the Delta Plus variant may be responsible for the third wave of COVID-19.
COVID-19 vaccine trials for children is being rapidly conducted in the country.
WHO Chief Scientist Dr. Soumya Swaminathan said that the data of Covaxin trial "looks good".
Covaxin has been found to be 65% effective against the delta variant of the COVID-19.
Covaxin has been found to be 77.8% effective in the third phase trial.
22 cases of delta plus variant of COVID-19 have been found in India.
The third phase trial of Covaxin was conducted on 25,800 people.