I work on statistical methods for evaluating biomarkers, or more broadly speaking, for evaluating tools for making medical decisions. Biomarkers may be used to screen or diagnose individuals with disease, to predict their risk of an adverse event or prognosis, or to predict benefit from an intervention. Many of the clinical contexts I work in are in the areas of cancer prevention or cancer treatment. I also work in the field of vaccine evaluation; I am a lead statistician for the HIV Vaccine Trials Network and in this capacity I develop and analyze HIV vaccine trials. This work involves a spectrum of research from collaborative analysis of immunology data to the design of sequential monitoring strategies for Phase III clinical trials.