Human challenge trials to test the efficacy of vaccine candidates against SARS-CoV-2, the novel coronavirus behind Covid-19, could save considerable time and many lives. But they may initially seem unethical because they expose healthy volunteers to a live virus that is killing many people and for which no cure exists. This article argues that this is not the correct test of their ethics. The correct test is comparative. And in the special circumstances of the Covid-19 pandemic, human challenge trials meet the correct test better than standard efficacy testing would.
Keywords: Covid-19; coronavirus; human challenge studies; randomized controlled trials; research ethics; risk taking; vaccines.
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