Both Covaxin and Covishield are the primary vaccine candidates approved for use in India. While Covishield is also approved for use in countries abroad, Covaxin is yet to be used globally.
The two vaccines, while both made using traditional vaccine-making technologies are slightly different in comparison. The Astrazeneca vaccine is an adenovirus vector and contains a weakened (harmless) version of the common cold virus, which has been further genetically modified to match the coronavirus (but cannot cause the illness). Meanwhile, Covaxin, makes use of an inactive strain, aka, a dead virus to instruct the immune cells to prompt an antibody response in the future run.
Since both the vaccines, though use a similar platform but work slightly differently in mimicking an immune response, experts opine the mixing benefits of both the vaccines could elicit a profoundly better immune response.
Talking about the efficacy and tolerability rates, both the vaccines also pass the WHO-approval norms. Preliminary studies and real-world observations have showcased that while Covaxin boasts of an efficacy rate that could vary between 70-81%, Covaxin, which has also been shown to considerably cut down rates of hospitalization and mortality with the disease, has an efficacy rate of 78%. The efficacy rates, however, do tend to come down with the Delta variant, but nonetheless, the vaccines are workable on many fronts.