Comparative Study in Healthy Adults Aged 18-50 Yrs Administered With Hepatyrix or Havrix+Typherix or Tiphim Vi, to Compare Reactogenicity & Immunogenicity

Inclusion criteria * Written informed consent will be obtained from the subject prior to entry into the study. * Free of obvious health problems as established by medical history and clinical examination before entering into the study. * Seronegative for anti-HAV antibodies. * If the subject is female, she must be of non-childbearing potential, i.e., either surgically sterilized or one year post-menopausal; or, if of childbearing potential, she must be abstinent or have used adequate contraceptive precautions (e.g., intrauterine contraceptive device; oral contraceptives; diaphragm or condom in combination with contraceptive jelly, cream or foam; Norplant® or DepoProvera®) for 30 days prior to vaccination, have a negative pregnancy test and must agree to continue such precautions for two months after completion of the vaccination series. * Subjects having received the study vaccines 36 months earlier. Exclusion criteria * Use of any investigational or non-registered drug or vaccine other than the study vaccine(s) within 30 days preceding the first dose of study vaccine, or planned use during the study period. * Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose. (For corticosteroids, this will mean prednisone, or equivalent, \>or = 0.5 mg/kg/day. Inhaled and topical steroids are allowed.). * Planned administration/Administration of a vaccine not foreseen by the study protocol within 30 days of the first dose of vaccine(s). * Administration of immunoglobulins and/or any blood products within the three months preceding the first dose of study vaccine or planned administration during the study period. * History of chronic alcohol consumption and/or intravenous drug abuse. * Previous vaccination against hepatitis A. * Previous vaccination against typhoid fever. * History of hepatitis A. * Previous diagnosis, confirmed by a physician, of Salmonella typhi infection. * History of non-response to hepatitis A and or typhoid vaccine. * Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection. * A family history of congenital or hereditary immunodeficiency. * History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. * Acute disease at the time of enrolment. (Acute disease is defined as the presence of a moderate or severe illness with or without fever. All vaccines can be administered to persons with a minor illness such as diarrhoea, mild upper respiratory infection with or without low-grade febrile illness, i.e., axillary temperature \< 99.5 °F (37.5 °C) * Female planning to become pregnant during the primary study period (up Month 7). * Pregnant or lactating female. * Planned travel to areas of high endemicity for hepatitis A and/ or typhoid fever during the primary study period (up Month 7).