CVD 909 Vi Prime Boost Study

Inclusion Criteria: Age 18 - 40 years, inclusive. Good general health as determined by a screening evaluation within 30 days before administration of CVD 909 or placebo. Expressed interest and availability to fulfill the study requirements. Informed, written consent. Agrees not to participate in another investigational vaccine or drug trial for the first 84 days of this study. Agrees not to become pregnant from the time of study enrollment until at least 56 days after the administration of CVD 909 or placebo; if a woman is sexually active and capable of conception (i.e., no history of hysterectomy or tubal ligation), she must agree to use hormonal or barrier birth control. A woman is eligible if she is monogamous with a vasectomized male. Exclusion Criteria: History of any of the following medical illnesses: Gall bladder disease or gall stones without cholecystectomy Diabetes Cancer Heart disease (hospitalization for a heart attack, arrhythmia, or syncope) Unconsciousness Seizures (other than febrile seizures as a child less than 5 years old) Recurrent infections (more than 3 hospitalizations for invasive bacterial infections such as pneumonia or meningitis) Any current illness requiring daily medication other than vitamins, birth control, or stable regimen of anti-histamine medication for hay fever or anti-depressant History of the following types of abdominal surgery: Any major gastrointestinal surgery (e.g., intestinal resection or splenectomy) A laparotomy for any reason (e.g., hysterectomy, Caesarean section, appendectomy, or herniorrhaphy) within the last 3 years Laparoscopic abdominal surgery within the past year A large abdominal scar of unclear origin Evidence of gastrointestinal disease, as indicated by any of the following: Usual bowel habit of more than 3 bowel movements each day Recurrent diarrhea (greater than 5 episodes during the past 6 months, each lasting at least 3 days, with at least one week between episodes) Lactose intolerance Frequent indigestion or heartburn that requires daily antacids or other medical therapy Diagnosed by a doctor as having irritable bowel disease, Crohn's disease, ulcerative colitis, celiac disease, stomach or intestinal ulcers in the past 10 years Blood in the stool during the past year (other than occasional small amount from straining) Any clinically significant abnormality detected on physical examination, including: Murmur (other than a functional murmur) Focal neurological deficit suggesting a pathologic process Hepatosplenomegaly Lymphadenopathy Jaundice Hypertension (BP greater than 150/90 mm Hg on two separate days) or hypotension (BP less than 85/55 mm Hg) Any lab abnormality, as listed below: WBC outside the normal range Hemoglobin outside the normal range Platelet count outside the normal range Creatinine outside the normal range Fasting glucose greater than 115 mg/dl (if screening greater than 115 mg/dl) AST or ALT outside the normal range (may be repeated once if outside this limit) Positive serology for hepatitis C or HIV antibody or hepatitis B surface antigen Stool culture positive for Salmonella spp, Shigella spp, Campylobacter jejuni, V. cholerae, or pathogenic protozoa For women, positive serum pregnancy test within 7 days and urine pregnancy test within 24 hours of administering CVD 909 and within 24 hours of administering Vi vaccine Nursing mother Oral temperature greater than 37.8ºC or symptoms of an acute self-limited illness such as an upper respiratory infection or gastroenteritis on the day of administration of CVD 909 or placebo Immunization against typhoid fever or history of typhoid fever Allergy to quinolones (including ciprofloxacin) or sulfa drugs (Including trimethoprim/sulfamethoxazole) Medical, occupational, or family problems as a result of alcohol or illicit drug use during the past 12 months Failure to pass written examination about study purpose, background, and procedures (70% correct answers required to pass) Receipt of an investigational vaccine or drug within 28 days before administration of CVD 909 Commercial food-handlers Health care workers who are engaged in patient care during the study Day care providers Subject with a household contact who is less than 2 years of age, who is immunocompromised or pregnant, or who works as a commercial food-handler Use of antibiotics within 7 days of CVD 909 or placebo vaccination Other condition that in the opinion of the investigator would jeopardize the safety or rights of a volunteer participating in the trial or would render the subject unable to comply with the protocol.