This editorial introduces articles in this Special Issue, which are based on presentations given at the 2017 meeting of the Global Forum of Bioethics in Research meeting. The main themes presented at the meeting were the use of cluster randomized trials, stepped-wedge cluster randomized trials, and controlled human infection models in research conducted in low-resource settings. The editorial sets out which ethical issues may arise in the context of alternative trial designs and describes the articles in this issue that addresses some or more of the ethical issues, such as justification of the research design, risk-benefit evaluations and consent.
Keywords: Adaptive trials; Alternative trial designs; Cluster randomized trials; Controlled human challenge studies; Ethics; Stepped wedge cluster randomized trials.