1. PCD Regulated Immunogenicity and Molecular, Merck and Co., Inc., West Point, PA 19486, USA
2. Current address: Janssen Pharmaceutical, Ambler, PA 19002, USA
3. Infectious Diseases and Vaccine Research, Merck and Co., Inc., West Point, PA 19486, USA
4. Analytical Research and Development, Merck and Co., Inc., West Point, PA 19486, USA
5. Current address: GSK Pharmaceutical, Collegeville, PA 19426, USA