If you did start experiments with those most vulnerable you exposing them to far more risks. Drug trials always start from learning more about safety of treatm

If you did start experiments with those most vulnerable you exposing them to far more risks. Drug trials always start from learning more about safety of treatment (as opposed to efficacy) and once deemed statistically safe, you move to test for efficacy. I assume you're thinking about treatments who could give a chance to those who have little hope/time for surviving. There's probably a chance they can benefit from taking experimental drugs but if we know little about it (because they are early in trial phases) we less confident this treatment will be useful and worst, we maybe not learn much from why it failed