1. Center of Infectious Disease Control, National Institute of Public Health and the Environment (RIVM), Bilthoven, the Netherlands
2. Virology Division, Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands
3. AstraZeneca, Gaithersburg, Maryland, USA
4. Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA