1. Division of Child and Adolescent Health, Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons , New York, New York , USA
2. Influenza Division, Centers for Disease Control and Prevention , Atlanta, Georgia , USA
3. Division of Pediatric Infectious Diseases, Department of Pediatrics, Columbia University Vagelos College of Physicians and Surgeons , New York, New York , USA
4. School of Nursing, Columbia University Irving Medical Center , New York, New York , USA
5. Department of Epidemiology, Mailman School of Public Health, Columbia University Irving Medical Center , New York, New York , USA
6. Department of Infection Prevention and Control, New York–Presbyterian Hospital , New York, New York , USA
7. Department of Population and Family Health, Mailman School of Public Health, Columbia University Irving Medical Center , New York, New York , USA