The Johns Hopkins CIR is looking for healthy volunteers to participate in an outpatient and inpatient Shigella and ETEC Vaccine study. The purpose of this study is to test an investigational oral vaccine call ShigETEC to prevent diarrheal illness cause by Shigella and ETEC bacteria that cause traveler's diarrhea. If you are between the ages of 18-50 you may be eligible to participate. The study is approximately 1 year and requires the following: