1. Department of Pediatrics, Division of Infectious Diseases Vanderbilt University Medical Center Nashville Tennessee USA
2. Department of Biostatistics Vanderbilt University Medical Center Nashville Tennessee USA
3. Pediatric Infectious Diseases, Institute for Infection, Inflammation, and Immunity in Children, University of Pittsburgh School of Medicine UPMC Children's Hospital of Pittsburgh Pittsburgh Pennsylvania USA
4. Primary Care Practice at Palm Center, Immunization Project, Baylor College of Medicine Texas Children's Hospital Houston Texas USA
5. Pediatrics and Molecular Virology and Microbiology, Baylor College of Medicine Texas Children's Hospital Houston Texas USA
6. Department of Pediatrics, Division of Infectious Diseases Seattle Children's Hospital Seattle Washington USA
7. Pathology & Laboratory Medicine Children's Mercy Hospital Kansas City Missouri USA
8. Pediatric Infectious Diseases, University of Cincinnati College of Medicine Cincinnati Children's Hospital and Medical Center Cincinnati Ohio USA
9. Pediatric Infectious Diseases University of Rochester Medical Center Rochester New York USA
10. Pediatric Infectious Diseases Children's Hospital and Research Center Oakland California USA
11. Department of Pediatrics, Division of Emergency Medicine Seattle Children's Hospital Seattle Washington USA
12. Department of Pediatrics, Section of Hematology‐Oncology, Baylor College of Medicine Texas Children's Hospital Houston Texas USA
13. Department of Pediatrics University of California at Los Angeles Mattel Children's Hospital Los Angeles California USA
14. Pediatric Infectious Diseases Children's Mercy Hospital Kansas City Missouri USA
15. National Center for Immunization and Respiratory Diseases, Division of Viral Diseases Centers for Disease Control and Prevention Atlanta Georgia USA
16. Epidemiology and Prevention Branch, Influenza Division, National Center for Immunization and Respiratory Diseases Centers for Disease Control and Prevention Atlanta Georgia USA