With all respect, this is glass half-empty mentality and a necessity vs sufficiency bias. The idea at this point is to take the risk and hopefully obtain meanin

With all respect, this is glass half-empty mentality and a necessity vs sufficiency bias. The idea at this point is to take the risk and hopefully obtain meaningful results. If the vaccine causes side effects with terminally-ill, then you have proof that it needs further evaluation and the sufficient condition is not met. If the vaccine, however, doesn't cause side effects and is proven efficient, it yeilds a sufficient result thus reducing the trial length, saving millions.