Jennifer Nelson is a biostatistician with expertise in methods to assess drug and vaccine safety and effectiveness. She is particularly interested in addressing statistical challenges that arise in studies that use large, observational health care data. Dr. Nelson provides national statistical leadership as the methods core co-lead and senior statistician for the Food and Drug Administration (FDA) Sentinel Initiative, an active electronic data surveillance system for monitoring the safety of all FDA-regulated medical products. She also serves as methodology committee chair for the Centers for Disease Control and Prevention-sponsored Vaccine Safety Datalink (VSD), a national collaboration involving 10 managed care organizations that has monitored immunization safety in the United States since 1990.