The purpose of this study is to evaluate the efficacy of the oral, live, attenuated ShigETEC vaccine against challenge with S. flexneri 2457T.
In Stage 1 of this study, ShigETEC vaccine or placebo will be administered orally to healthy participants at a dose of 5x10\^10 CFU. This dose was tested in a Phase 1 trial and found to be safe when given 4 times with an interval of 3 days between each dose.
The efficacy of ShigETEC vaccination will be evaluated in Stage 2 of this study, when participants will be challenged with S. flexneri 2457T.
The study population will be healthy adult participants in the age of 18-50 years (inclusive), which are clearly defined in the study protocol.
Generally healthy non-pregnant, non-nursing adults aged 18 to 50 years.
Who are determined by medical history, physical examination, laboratory testing, and clinical judgment to be eligible for this study.
Who provide written informed consent after the nature of the study had been explained.
Who are available for the duration of the trial (from enrollment to study completion).
Participants who are perceived to be unavailable or difficult to contact for evaluation or study visits during the study period.
Presence of a significant medical or psychiatric condition which in the opinion of the Investigator precludes participation in the study.
Clinically significant abnormalities in screening hematology or serum chemistry, defined as > grade 1 abnormality of serum potassium, alanine aminotransferase (ALT) or creatinine, hemoglobin, white blood cell count (WBC), or neutrophil count.
Who have received any blood products, including immunoglobulin, in the period from 6 months prior to vaccination or are anticipated to receive such products through to the conclusion of the study and have not donated blood within 30 days and agree not to donate blood until 1 year after challenge.