Shigella CVD 31000: Study of Responses With Shigella-ETEC Vaccine Strain CVD 1208S-122

Inclusion Criteria: * Male or female, 18 - 49 years of age * Written informed consent provided * Determined to be in good health\* based on medical history and review of concomitant medications \*Good health as defined by an absence of an active chronic medical condition which requires daily prescription medication(s). Participants may be eligible if the medical condition only requires infrequent as needed (PRN) medication and if the investigator determines that the condition does not pose a risk to participant safety or the assessment of reactogenicity and immunogenicity. Any chronic medical condition which does not require a daily prescription medication but might pose a risk to a participant with rapid dehydration (i.e., rapid intravascular volume changes) would be ineligible to participate. * Documented acceptable results from screening laboratory work (defined in Appendix B), including: * Complete blood count (CBC) with differential for total white blood cell count (WBC), absolute neutrophil count (ANC), hemoglobin (Hg), platelet count * Creatinine, alanine aminotransferase (ALT), total bilirubin * Serum Immunoglobulin A (IgA) level * Human immunodeficiency virus (HIV) antibody, Hepatitis B surface antigen (HBsAg), Hepatitis C virus antibody (HCV) * HLA-B27 histocompatibility testing * Serum Beta human chorionic gonadotropin (β-HCG) test, if the participant is a woman of child-bearing potential * A passing score (≥70%) on a Comprehension Assessment Tool * Agrees not to participate in another clinical trial during the study period * Females of child-bearing potential† agree to use an acceptable form of birth control‡ from enrollment and through at least 4 weeks after vaccination †Females of child-bearing potential, defined as having not been sterilized via tubal ligation, bilateral oophorectomy, salpingectomy, hysterectomy, or successful Essure® placement (permanent, non-surgical, non-hormonal sterilization) with documented radiological confirmation test at least 90 days after the procedure, and still menstruating or \<1 year has passed since the last menses, if menopausal. ‡Acceptable birth control includes barrier methods such as condoms or diaphragms/cervical cap with spermicide; effective intrauterine devices; NuvaRing®; and licensed hormonal methods such as implants, injectables or oral contraceptives ("the pill") or alternatively, monogamous relationship with a vasectomized partner who has been vasectomized for 180 days or more prior to the subject receiving the study vaccination, abstinence from sexual intercourse with a male partner, or sexual relationships with non-male partners. * Available for up to a 6-day inpatient stay * For Participants of Cohorts 1-3 during the time when a U.S. Public Health Emergency for COVID-19 exists, SARS-CoV-2 testing must be performed upon admission to the inpatient ward and must document a negative test result prior to vaccination. Exclusion Criteria: * A positive pregnancy test at screening or within 24 h prior to study product dosing * A female who is breastfeeding * Poor venous access, as defined by inability to obtain venous blood, for screening labs, after 3 venipuncture attempts * Abnormal vital signs, defined as: * Systolic BP \>150 mmHg or Diastolic BP \>90 mmHg * Resting heart rate \>100 bpm * Oral temperature ≥38.0°C * Having received prior vaccines for or have had prior infection with ETEC, LT, cholera, or Shigella, within the past 3 years * History of diarrhea during travel to a developing country within the past 3 years * History of chronic gastrointestinal illness, including severe dyspepsia, lactose intolerance, or another significant gastrointestinal tract disease (e.g., irritable bowel syndrome, inflammatory bowel syndrome, gastric ulcer disease) * Regular use (≥once weekly) of laxatives, anti-diarrheal agents, anti-constipation agents, or antacid therapies * History of major gastrointestinal surgery (uncomplicated laparoscopic appendectomy or cholecystectomy \>1-year prior is permitted) * Abnormal bowel habits, as defined by \<3 stools per week or \>2 stools per day in the past 6 months * Use of systemic antimicrobials§ within the past 2 weeks * use of topical (skin), otic, or ophthalmic antibiotics is acceptable, if those doses are not expected to result in significant systemic absorption levels * Use of oral, parenteral or high-dose inhaled steroids within 30 days * Use of any medication which might affect immune function# within 30 days #examples include anti-cancer drugs, immunomodulating monoclonal antibody therapeutics, and rheumatologic therapies * Diagnosis of schizophrenia or other major psychiatric disease * Alcohol or drug abuse within last 5 years * Presence of immunosuppression, which could be due to active neoplastic disease or a history of any hematologic malignancy (excluding resolved non-melanoma skin cancers), radiation therapy, or primary or secondary immunodeficiencies * History of allergy to quinolone (e.g., ciprofloxacin) or sulpha drugs (e.g., trimethoprim-sulfamethoxazole) * Known history of seizure disorder (remote history of a childhood seizure disorder which has completely resolved is acceptable) * Occupation involving the handling of ETEC, cholera, or Shigella bacteria * Occupation in food handling industry or care of very young children (\<2 years old), elderly (≥70 years), or immunocompromised * During the time when a U.S. Public Health Emergency for COVID-19 exists, within 14 days prior to the time of vaccination, the presence of 2 or more of any of the following symptoms: fever (≥38°C, chills, myalgia, headache, sore throat, or new olfactory and taste disorder * During the time when a U.S. Public Health Emergency for COVID-19 exists, within 14 days prior to the time of vaccination, the presence of 1 or more of any of the following respiratory symptoms: cough which cannot otherwise be explained, shortness of breath, or difficulty breathing * Any other criteria which, in the investigator's opinion, would compromise the safety of the study, the ability of a subject to participate, or the results of the study