It is not as if people have a choice on which vaccine to take. There are no studies done on the impact of taking a third dose of a different vaccine if that is what you are suggesting, besides it impacts the vaccine availability even more if people vaccinated with 2 doses of Covaxin now decide to take Covishield.Please do share sources for people after taking covaxin 2 doses are getting critical?
Covidshield is very effective after two doses if you're worried covaxin isn't effective just take the covidshield.
In general, most company-organised vaccination drives are insisting only on Covishield, partly because Covaxin may also affect international travel as it is not recognised by WHO.
Meanwhile, I had people from my organisation affected by Covid-19 in the recent wave taking their vaccine from private hospitals just after a month because they want a vaccination certificate, despite studies emphasizing that having the vaccination soon after infection produces very little antibodies. There is no limit to stupidity.