Conventional vaccine testing is a slow, years-long process. As thousands of people continue to die each day from COVID-19, bioethicist Nir Eyal proposes a radical idea that could dramatically accelerate the vaccine development timeline: "human challenge trials," in which scientists would deliberately expose volunteers to the virus to more quickly determine a vaccine's efficacy. (This virtual conversation, hosted by head of TED Chris Anderson, was recorded June 15, 2020.)