Two critical, recurring questions can arise in many areas of research with human subjects but are poorly addressed in much existing research regulation and ethics oversight: How should research risks to “bystanders” be addressed? And how should research be evaluated when risks are substantial but not offset by direct benefit to participants, and the benefit to society (“social value”) is context-dependent? We encountered these issues while serving on a multidisciplinary, independent expert panel charged with addressing whether human challenge trials (HCTs) in which healthy volunteers would be deliberately infected with Zika virus could be ethically justified (1). Based on our experience on that panel, which concluded that there was insufficient value to justify a Zika HCT at the time of our report, we propose a new review mechanism to preemptively address issues of bystander risk and contingent social value.