Ebola vaccine candidates against Ebola have been developed in the decade prior to 2014, but none have yet been approved for clinical use in humans. Several promising vaccine candidates have been shown to protect nonhuman primates (usually macaques) against lethal infection. These include replication-deficient adenovirus vectors, replication-competent vesicular stomatitis (VSV) and human parainfluenza (HPIV-3) vectors, and virus-like nanoparticle preparations. Conventional trials to study efficacy by exposure of humans to the pathogen after immunization are obviously not feasible in this case. For such situations, the FDA has established the "Animal Efficacy Rule" allowing licensure to be approved on the basis of animal model studies that replicate human disease, combined with evidence of s