A Study to Evaluate the Efficacy, Safety and Immunogenicity of a Vaccine Designed to Protect Against Infection With Shigella Sonnei in Healthy Adults

Inclusion Criteria

• Subjects who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
• Written informed consent obtained from the subject prior to performing any study specific procedure.
• Individuals who, after the nature of the study has been explained to them, have shown adequate comprehension of the study procedures and knowledge of study.
• A male or female between, and including, 18 and 50 years of age at the time of the first vaccination.
• Healthy subjects as established by medical history and clinical examination before entering into the study.
• Seronegative for human immunodeficiency virus (HIV), hepatitis B and C.
• Female subjects of non-childbearing potential may be enrolled in the study.
• Female subjects of childbearing potential may be enrolled in the study, if the subject:
• Has practiced adequate contraception for 30 days prior to vaccination, and
• Has a negative pregnancy test on the day of vaccination, and
• Has agreed to continue adequate contraception during the entire study period.

Exclusion Criteria

• Received an investigational or non-registered medicinal product within 30 days prior to informed consent, or planned use during the study period.
• Any behavioral or cognitive impairment or psychiatric disease that, in the opinion of the investigator, may interfere with the subject's ability to participate in the study.
• History of any neurological disorders or seizures.
• Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the subject due to participation in the study.
• Human Leukocyte Antigen (HLA)-B27 positive test at screening and/or with history of reactive arthritis.
• Clinical conditions representing a contraindication to intramuscular vaccination and blood draws.
• Chronic administration of immunosuppressants or other immune-modifying drugs during the period starting six months prior to the first vaccine/placebo dose. For corticosteroids, this will mean prednisone ≥ 20 milligrams (mg)/day, or equivalent. Inhaled except for doses > 800 µg/day and topical steroids are allowed.
• Administration of long-acting immune-modifying drugs at any time during the study period. Subjects may be on chronic or as needed medications if, in the opinion of the site principal investigator or appropriate sub-investigator, they pose no additional risk to subject safety or assessment of reactogenicity and immunogenicity and do not indicate a worsening of medical diagnosis or condition.
• Known bleeding diathesis or any condition that may be associated with a prolonged bleeding time.
• Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational vaccine/product.
• History of having participated in a previous Shigella challenge study.
• Individuals who have a previously laboratory confirmed case of disease caused by S. sonnei or serology positive for local anti S. sonnei LPS IgG Screening-ELISA at screening.
• History of any serious chronic or progressive disease according to judgment of the investigator.
• History of any malignancy or lymphoproliferative disorder.
• Known to be part of study personnel or being a close family member to the personnel conducting this study.
• History of anaphylactic reaction or allergy to vaccine/placebo or challenge agent components or any other allergies deemed by the investigator to increase the risk of an AE if they were to participate in the study.
• Known allergy to ciprofloxacin or the other antibiotics used for treatment as deemed by the investigator.
• Individuals receiving a course of antibiotics within a week of the challenge will be ineligible to receive the challenge strain.
• History of gastric acid hyper-secretory disorders as assessed and judged by the investigator or any other significant intestinal disorder.
• Any confirmed or suspected immunosupp