The purpose of this study is to assess the immune response produced by two doses of SC599 vaccine compared to placebo.

Inclusion Criteria:

• Adult volunteers age 18 to 50
• Signed Informed Consent form following a detailed written explanation of participation in the protocol
• Volunteers who are in good health as determined by medical history, physical examination and clinical judgement
• Volunteers who will be available and "normally reside within the M25" (England) or in Paris and Paris suburb (France) and not leave England or France for the duration of the study
• Women who agree to have a pregnancy test immediately before immunisation and to use effective contraception during the study period
• Volunteers eligible for free NHI treatment (England), volunteers who are covered by social security (France)

Exclusion Criteria:

• Individuals who have hypersensitivity to any component of the vaccines used in this study.
• Individuals who have hypersensitivity to ciprofloxacin
• Individuals who are found to be HIV or HCV antibody positive or Hepatitis B surface antigen positive at the time of initial screening
• Individuals who are found to have HLA-B27 tissue type at the time of initial screening
• Individuals with a known or suspected history of gastrointestinal disease or abnormality
• Concomitant therapy with antibiotics, iron, zinc, H2-receptor antagonists or proton pump inhibitors
• Individuals who have received any vaccine against Shigella or had proven or suspected shigellosis (bloody diarrhoea with fever) within 6 months prior to study entry
• Individuals with a significant level of immunity against Shigella detected at the screening visit (defined as serum ELISA anti-LPS IgG antibody titre greater than 3 S.D. above the mean background activity of a bank of healthy human sera)
• A Clinically significant amount of protein or haemoglobin in the urine sample at the screening visit
• A Clinically significant abnormality in the haematological or biochemical assays (an abnormal value will be defined by the ranges quoted in each centre) at the screening visit
• A positive Shigella stool culture at the screening visit
• Individuals with a known impairment of immune function or those receiving immunosuppressive therapy (including systemic corticosteroids). Inhaled or topical steroid preparation are not a non-inclusion criterion
• Individuals with acute infections (including fever > 37.5°C oral temperature)at the time of immunisation or any chronic disease
• Women capable of becoming pregnant who do not agree to have pregnancy testing before immunisation, or who do not agree to take effective contraception during the study period
• Breastfeeding women
• Individuals with a current problem with substance abuse or with a history of substance abuse which in the opinion of the investigator, might interfere with participation in the study
• Individuals with any condition which, in the opinion of the investigator, might interfere with the evaluation with the study objectives
• Individuals who have received an investigational product within 30 days prior to entry
• Individuals who cannot read, speak fluent French or English according to the investigational site setting
• Individuals who are planning to leave England or France prior to the end of the study period or who are likely not to complete the study
• Individuals who have persons living with them who in the opinion of the investigator may be at risk of disease if exposed to the vaccine strain or whose occupation may bring them into contact with persons at risk of disease or who are food handlers by occupation
• Individuals with close household contact with child younger than 5 years or a person with immunodeficiency