We know that Most vaccines against SARS-CoV-2 must be given in two doses, but the idea of mix and match came about the variable efficacy of different vaccines and the problem of side effects.

It’s called heterologous prime-boost vaccination: it’s where instead of first (“prime”) and second (“boost”) injection of the same vaccine, they’re 2 different ones – or perhaps a second boost (third shot) is another vaccine.

The theory is that this could widen immune responses more than same-same vaccination, as vaccines are targeted at stimulating the immune
system in different ways.

Is it possible and safe for patients to be given the 2 doses of Sinovac then mRNA Vaccine like Pfizer as third booster shot?

Data from this video include newspaper clipping from different news sources including Reuters, and a tweet of Dr Eric Feign-Ding.