1. Department of Health Policy , Vanderbilt University Medical Center, Nashville, Tennessee , USA
2. Department of Biostatistics , Vanderbilt University Medical Center, Nashville, Tennessee , USA
3. Department of Pediatrics, Vanderbilt University Medical Center , Nashville, Tennessee , USA
4. Department of Medicine, University of Tennessee College of Medicine , Nashville, Tennessee , USA
5. Influenza Division, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention , Atlanta, Georgia , USA
6. Department of Medicine , Vanderbilt University Medical Center, Nashville, Tennessee , USA
7. Department of Biomedical Informatics, Vanderbilt University Medical Center , Nashville, Tennessee , USA