“If we start just using it on everyone, we’re not going to learn what we need to know.” That’s one side of a fierce debate over using Ervebo, a vaccine against Ebola Zaire, in the current outbreak caused by a different virus, Bundibugyo. The other: waiting for perfect evidence could cost lives. https://www.science.org/content/article/mismatched-vaccine-being-rolled-out-against-ebola-outbreak