Immunogenicity and Safety of Meningococcal Vaccine GSK 134612 Versus Mencevax™ ACWY in Healthy 18-25 Year Olds

Inclusion Criteria: All subjects must satisfy all of the following criteria at study entry: * Subjects whom the investigator believes they can and will comply with the requirements of the protocol will be enrolled in the study. * A male or female between, and including, 18 and 25 years of age the time of the vaccination. * Written informed consent obtained from the subject. * Healthy subjects as established by medical history and clinical examination before entering into the study. * 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 treatment period and for 2 months after vaccination. Exclusion Criteria: The following criteria should be checked at the time of study entry. If any exclusion criterion applies, the subject must not be included in the study: * Use of any investigational or non-registered product other than the study vaccine(s) within 30 days preceding the dose of study vaccine, or planned use during the study period. * Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to vaccination. (For corticosteroids, this will mean prednisone \<10 mg/day, or equivalent, is allowed. Inhaled and topical steroids are allowed). * Planned administration/administration of a vaccine not foreseen by the study protocol within one month of the dose of vaccine, with the exception of any licensed inactivated influenza vaccine, including H1N1 vaccine. * Previous vaccination with meningococcal polysaccharide vaccine within the last five years. * Previous vaccination with meningococcal conjugate vaccine. * Previous vaccination with tetanus-toxoid or tetanus-toxoid containing vaccine within the last month. * History of meningococcal disease. * Seropositive for HIV or HBsAg (for subjects in the Philippines only). * Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus infection, based on medical history and physical examination. * A family history of congenital or hereditary immunodeficiency, until the immune competence of the potential vaccine recipient has been demonstrated. * History of reactions or allergic disease likely to be exacerbated by any component of either vaccine. * History of any neurologic disorders, including Guillain-Barré Syndrome. * Major congenital defects or serious chronic illness. * Acute disease at the time of enrolment. * Administration of immunoglobulins and/or any blood products within the three months preceding the dose of study vaccine or planned administration during the study period. * Pregnant or lactating female. * History of chronic alcohol consumption and/or drug abuse. * Female planning to become pregnant or planning to discontinue contraceptive precautions. * Bleeding disorders, such as thrombocytopenia, or subjects on anti-coagulant therapy. * 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 product.