Evaluation of Safety and Immunogenicity of GSK Bio's Influenza Vaccine GSK576389A After Repeated Vaccination in Elderly Adults

Inclusion Criteria: * Subjects who were previously vaccinated with GlaxoSmithKline Biologicals Fluarix™ or GSK576389A investigational vaccines in the 104887 study (NCT00386698). * Subjects who the investigator believes that they can and will comply with the requirements of the protocol should be enrolled in the study. * A male or female aged between 19 and 42 years or 66 years and older at the time of the vaccination. * Written informed consent obtained from the subject. * Free of an acute aggravation of the health status as established by clinical evaluation before entering into the study. * If the subject is female, she must be of non-childbearing potential or if she is of childbearing potential, she must practice adequate contraception for 30 days prior to vaccination, have a negative pregnancy test and continue such precautions for 2 months after completion of the vaccination series. Exclusion Criteria: * Use of any investigational or non-registered product (drug or vaccine) other than the study vaccines within 30 days prior to vaccination, or planned use during the study period. * Administration of other licensed vaccines within 2 weeks (for inactivated vaccines) or 4 weeks (for live vaccines) prior to enrolment in this study. Planned administration of a vaccine not foreseen by the study protocol up to 21 days after vaccination. * Planned administration of an influenza vaccine other than the study vaccines during the entire study period. * Vaccination against influenza since January 2007 with the Northern Hemisphere 2007/2008 influenza vaccine or 2006/2007 influenza vaccine. * History of confirmed influenza infection since the date of previous vaccination. * Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within six months prior to the administration of the study vaccine. (For corticosteroids, this will mean prednisone, or equivalent, ≥0.5 mg/kg/day. Inhaled and topical steroids are allowed.) * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required). * History of hypersensitivity to a previous dose of influenza vaccine. * History of allergy or reactions likely to be exacerbated by any component of the vaccine(s) * Acute (active) clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by clinical evaluation (medical history and medical history directed physical examination) or pre-existing laboratory screening tests. * 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 diarrhea, mild upper respiratory infection with or without low-grade febrile illness, i.e. Axillary temperature \<37.5°C / Oral temperature of \<37.5°C). * Administration of immunoglobulins and/or any blood products within the three months preceding the first administration of the study vaccine or planned administration during the study. * Any medical conditions in which intramuscular injections are contraindicated. * Pregnant or lactating female. * Female planning to become pregnant or planning to discontinue contraceptive precautions.