Since 2006, he has served as the Director of the Center for the History of Medicine based at the Countway Medical Library. He has co-authored Generation of Diversity: Clonal Selection Theory and the Rise of Molecular Immunology (1997), authored Pneumonia before Antibiotics: Therapeutic Evolution and Evaluation in Twentieth-Century America (2006), and co-edited Oliver Wendell Holmes: Physician and Man of Letters (2009). His forthcoming book, The Antibiotic Era: Reform, Resistance, and the Pursuit of a Rational Therapeutics, will be published by Johns Hopkins University Press in January of 2015.