The preliminary scientific evidence submitted by the Christian Medical College, Vellore, to the Drugs Controller General of India (DCGI)suggested that a booster dose of Covishield after two doses of Covaxin enhanced the immunity six times.But, satisfactory data was not available for administering Covaxin as a precaution dose after two doses of Covishield.

The study conducted by CMC Vellore is the first Indian evidence stating the impact of mixing of vaccines on COVID. The study was approved by the DCGI in September 2021.

Reports stated that the National Technical Advisory Group on Immunisation (NTAGI) would take the decisionon administering a different vaccine as the third dose based on the final data. 

Meanwhile, various other studies are being conducted which are studying the effects of mixing Corbevax, Covavax and Biotechs intranasal vaccine. (ET HealthWorld - TOI; March 18, 2022)