1. Medicine, Infectious Diseases, University of Pittsburgh, Pittsburgh, PA, USA
2. Epidemiology, University of Michigan, Ann Arbor, MI, USA
3. Pediatrics, Pediatric Infectious Diseases, Baylor Scott and White, Austin, TX, USA
4. Kaiser Permanente Washington Health Research Institute, Seattle, WA, USA
5. Center for Clin Epidemiology & Population Health, Marshfield Clinic Research Institute, Marshfield, WI, USA
6. Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA