Polio had trials too. I had a coworker who participated in one and he got the placebo, got polio and now has a withered left arm. At least he didn’t end up in an iron lung. He was pretty pissed he ended up a guinea pig.
I don’t know how long ago the trials you mention took place. However, by now I would think that when an effective vaccine/cure for a serious condition is proven in a trial, then the placebo folks should be given the opportunity to also receive the treatment. If this is not now the case, then some laws need to be enacted.