Norwalk Vaccine Study

Inclusion criteria

• . Signed informed consents.
• . Age 18 - 50 years, inclusive.
• . Good general health as determined by a screening evaluation within 45 days of randomization.
• . Expressed interest, availability, and understanding to fulfill the study requirements including measures to prevent Norwalk virus contamination of the environment and spread of infection and illness to the community. The prospective subjects must pass (\> 75 % correct answers) a written examination on all aspects of the study before enrollment. (Appendix D)
• . Available to return for follow-up visits following discharge from the inpatient unit and deliver stool specimens to the investigator promptly.
• . Female subjects must be of non-childbearing potential, or if of childbearing potential (as determined by the investigator) must be practicing abstinence or using an effective licensed method of birth control (e.g. oral contraceptives; diaphragm or condom in combination with contraceptive jelly, cream, or foam; intrauterine contraceptive device, or Depo-Provera; skin patch; vaginal ring or cervical cap) for 30 days prior to vaccination and must agree to continue such precautions during the study and for 60 days after the Challenge visit. Male subjects must agree not to father a child during the study and for 60 days after the Challenge visit.
• . Demonstrated to be H type-1 antigen secretor positive (by saliva test). \[This saliva test may be done outside of the 45 day window and does not need to be repeated.\]
• . Agrees not to participate in another clinical trial with an investigational product for the entire duration of the study (six months after the last dose of study vaccine or placebo i.e. 201 days).