Author information:
(1)Division of Infectious Diseases, Department of Medicine, Perelman School of 
Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; Center for 
Clinical Epidemiology and Biostatistics, Department of Biostatistics and 
Epidemiology, Perelman School of Medicine, University of Pennsylvania, 
Philadelphia, Pennsylvania; Center for Pharmacoepidemiology Research and 
Training, Perelman School of Medicine, University of Pennsylvania, Philadelphia, 
Pennsylvania. Electronic address: vincentl@mail.med.upenn.edu.
(2)Center for Clinical Epidemiology and Biostatistics, Department of 
Biostatistics and Epidemiology, Perelman School of Medicine, University of 
Pennsylvania, Philadelphia, Pennsylvania; Center for Pharmacoepidemiology 
Research and Training, Perelman School of Medicine, University of Pennsylvania, 
Philadelphia, Pennsylvania.
(3)Center for Clinical Epidemiology and Biostatistics, Department of 
Biostatistics and Epidemiology, Perelman School of Medicine, University of 
Pennsylvania, Philadelphia, Pennsylvania; Center for Pharmacoepidemiology 
Research and Training, Perelman School of Medicine, University of Pennsylvania, 
Philadelphia, Pennsylvania; Division of Gastroenterology, Department of 
Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, 
Pennsylvania.
(4)Center for Clinical Epidemiology and Biostatistics, Department of 
Biostatistics and Epidemiology, Perelman School of Medicine, University of 
Pennsylvania, Philadelphia, Pennsylvania; Division of Gastroenterology, 
Department of Medicine, Perelman School of Medicine, University of Pennsylvania, 
Philadelphia, Pennsylvania.
(5)Center for Clinical Epidemiology and Biostatistics, Department of 
Biostatistics and Epidemiology, Perelman School of Medicine, University of 
Pennsylvania, Philadelphia, Pennsylvania.
(6)Center for Pharmacoepidemiology Research and Training, Perelman School of 
Medicine, University of Pennsylvania, Philadelphia, Pennsylvania; Division of 
Gastroenterology, Department of Medicine, Perelman School of Medicine, 
University of Pennsylvania, Philadelphia, Pennsylvania.
(7)Division of Research, Kaiser Permanente Northern California, Oakland, 
California.
(8)Center for Clinical Epidemiology and Biostatistics, Department of 
Biostatistics and Epidemiology, Perelman School of Medicine, University of 
Pennsylvania, Philadelphia, Pennsylvania; Center for Pharmacoepidemiology 
Research and Training, Perelman School of Medicine, University of Pennsylvania, 
Philadelphia, Pennsylvania; Rutgers Biomedical & Health Sciences, Rutgers, the 
State University of New Jersey, Newark, New Jersey.