Immunogenicity and Safety of Meningococcal Vaccine GSK134612 Given as 1 or 2 Doses to Healthy 9-12 Months old Toddlers.

•Subjects whose parents/guardians the investigator believes can and will comply with the requirements of the protocol •A male or female of 9 months of age (has not attained 10 months of age) at the time of enrollment. •Up to date on vaccinations based on ACIP recommendations and the standard practice at the investigational site. •Written informed consent obtained from parents/guardian of the subject. •Healthy subjects as established by medical history and clinical examination before entering into the study.

•Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine(s) within 30 days preceding enrollment, 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 vaccine dose. •Planned administration/ administration of a vaccine not foreseen by the study protocol within 1 month of a dose of study vaccine(s), with the exception of influenza vaccine. •Planned administration of a tetanus toxoid (TT) containing vaccine throughout the active phase of the study (through one month after the last vaccination). •Previous vaccination with meningococcal polysaccharide or conjugate vaccine of serogroup A, C W and/or Y. •History of meningococcal diseases. •Any confirmed or suspected immunosuppressive or immunodeficient condition (congenital or secondary), including human immunodeficiency virus (HIV) infection, based on medical history and physical examination (no laboratory testing is required). •A family history of congenital or hereditary immunodeficiency, until the immune competence of the potential vaccine recipient is demonstrated. •History of reactions or allergic disease likely to be exacerbated by any component of the vaccine. •Major congenital defects or serious chronic illness. •History of any neurologic disorders or seizures. •Acute disease at the time of enrollment. •Administration of immunoglobulins and/or any blood products within the three months preceding the first dose of study vaccine or planned administration during the active phase of the study (through one month after the last dose of study vaccine).