Charles Weijer is a professor of Medicine, Epidemiology, and Biostatistics, and of Philosophy at Western University in London, Canada, where he teaches bioethics. His research addresses the ethics of randomized controlled trials. In 2012, he was the lead author of the “The Ottawa Statement on the Ethical Design and Conduct of Cluster Randomized Trials,” the first international ethical guidelines for cluster trials. In 2020, he served on the World Health Organization’s Working Group for Guidance on Human Challenge Studies in COVID-19. His current work explores ethical issues in pragmatic trials that evaluate health interventions in real-world conditions to better inform patients, health providers, and health systems managers.