1. Division of Viral Products, Center for Biologics Evaluation and Research, FDA, Silver Spring, Maryland, USA
2. Department of Zoology, University of Cambridge, Cambridge, United Kingdom
3. Department of Medicine, University of Chicago, Chicago, Illinois, USA
4. Laboratory of Infectious Diseases, NIAID, National Institutes of Health, Bethesda, Maryland, USA
5. Influenza Division, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
6. National Institute of Biological Standards and Control, MHRA, South Mimms, United Kingdom
7. Emory Vaccine Center, Department of Microbiology and Immunology, Emory University School of Medicine, Atlanta, Georgia, USA
8. Department of Virology, Erasmus Medical Center, Rotterdam, Netherlands