> From an ethical viewpoint, this is incredibly wrong, as vaccines given to healthy people which cause problems later are very very dangerous.
The first two phases are the safety tests, the third one is efficacy (so we knew the vaccine was "safe" after phase 2, we just didn't know the efficacy - that's what the poster above is alluding to).
The first two phases are the safety tests, the third one is efficacy (so we knew the vaccine was "safe" after phase 2, we just didn't know the efficacy - that's what the poster above is alluding to).