After the Phase 1 data was back, arguably it wouldn’t have been a bad call to give doses for free and gamble on the efficacy even if it turned out to be below 50%.
> 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).