While the first phase will test 1000 people, the second phase of the trial will have a bigger number, which ultimately depends on the final outcome of the study. The estimated time frame for clinical trials is expected to be 6-8 months.

from Times of India https://timesofindia.indiatimes.com/life-style/health-fitness/health-news/indias-first-coronavirus-vaccine-covaxin-to-start-human-trials-this-week/articleshow/76848297.cms