Biomarkers have been used historically to monitor disease incidence and prevalence, measure immune responses to natural infection or vaccination and to determine the duration of immunity. This talk will discuss how antibody and functional biomarker assays are being implemented to accelerate phase I vaccine/antibody studies, dose ranging studies, evaluate adjuvants, licensure studies, concomitant vaccine studies, phase IV marketing studies and post-licensure surveillance studies. Specific examples of how biomarkers were used in the development and post-licensure marketing studies of FluMist® and Synagis® will be reviewed.