They could find 200 volunteers who had taken both doses of Covishield—the maximum number needed.
The next phase of the study is to test the efficacy of a booster dose of Covaxin on volunteers who took two doses of Covishield and vice versa.
The 18-month long study will later use other government of India-approved vaccines to test efficacy.
Asked whether Russia’s Sputnik, the only vaccine other than Covaxin and Covishield approved by Inida, would be one such candidate he said, “No, we will not use Sputnik as it is very similar to Covishield. Additional new vaccines which enter the field and are approved by the union government will become p