1. Department of Medicine, Stanford University School of Medicine, California
2. Vaccine Testing Center, University of Vermont College of Medicine, Burlington
3. Division of Infectious Diseases and Vaccinology, School of Public Health, University of California, Berkeley
4. Laboratorio Nacional de Virología, Centro Nacional de Diagnóstico y Referencia, Ministry of Health, Managua, Nicaragua
5. Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore
6. Laboratory of Infectious Diseases, National Institute for Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
7. Department of Microbiology and Immunology, Stanford University School of Medicine
8. Veterans Affairs Palo Alto Health Care System, California