1. From the University of Maryland School of Medicine, Baltimore, Maryland;
2. National Institute of Allergy and Infectious Diseases, National Institute of Health, Bethesda, Maryland;
3. University of Rochester School of Medicine, Rochester, New York;
4. Baylor College of Medicine, Houston, Texas;
5. Center for Biologicals Evaluation and Research, Food and Drug Administration, Bethesda, Maryland;
6. St Louis University School of Medicine, St Louis, Missouri;
7. Johns Hopkins School of Public Health, Baltimore, Maryland;
8. Vanderbilt University School of Medicine, Nashville, Tennessee.