1. Influenza Division; National Center for Immunization and Respiratory Diseases; CDC; Atlanta GA USA
2. Marshfield Clinic Research Institute; Marshfield WI USA
3. Baylor Scott & White Health; Texas A&M University Health Science Center College of Medicine; Temple TX USA
4. University of Pittsburgh Schools of the Health Sciences and University of Pittsburgh Medical Center; Pittsburgh PA USA
5. Kaiser Permanente Washington Health Research Institute; Seattle WA USA
6. University of Michigan; Ann Arbor MI USA