India’s Bharat Biotech has finalized enrollment for a phase 3 trial of its COVID-19 vaccine, Covaxin, which Indian regulators approved Jan. 3 for emergency use.

The study, involving almost 26,000 participants, is the largest phase 3 vaccine trial ever conducted in India, Bharat says. According to ClinicalTrials.gov, the phase 3 study has an expected primary completion date of June 30 and a study completion date of March 1, 2022.

The two-dose vaccine was previously evaluated in approximately 1,000 volunteers in early-stage trials, where it demonstrated positive immunogenicity and safety.

Vaccine experts have questioned India’s emergency approval in the absence of reliable data from the late-stage trial, which only got under way in mid-November.