The 2014 Ebola virus epidemic is the largest and most severe ever recorded. With no approved vaccines or specific treatments for Ebola, clinical trials were launched within months of the epidemic in an unprecedented show of global partnership. One of these trials used a highly innovative "ring vaccination" design. The design was chosen for operational, scientific, and ethical reasons--in particular, it was regarded as ethically superior to individually randomized placebo-controlled trials. We scrutinize the ethical rationale for the ring vaccination design. We argue that the ring vaccination design is ethical but fundamentally equivalent to placebo-controlled designs with respect to withholding a potentially effective intervention from the control group. We discuss the implications for the ongoing ring vaccination trial and future research.