Study to Evaluate the Safety and Immunogenicity of GlaxoSmithKline Biologicals' Influenza Vaccine in Elderly People

Inclusion Criteria: All subjects must satisfy ALL the following criteria at study entry: * Subjects who the investigator believes that they can and will comply with the requirements of the protocol should be enrolled in the study. Specific attention should be given to the compliance potential of subjects with suspected drug or alcohol abuse. * A male or female aged 19-43 years or \>=66 years at the time of the vaccination and who participated in the study NCT00760617 and completed the 6-month follow-up. * 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. * Female subjects of non-childbearing potential may be enrolled in the study. * Non-childbearing potential is defined as pre-menarche, current tubal ligation, hysterectomy, ovariectomy or post-menopause. * 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 for 2 months after the 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 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 an influenza vaccine other than the study vaccines or of a vaccine not foreseen in the study protocol during the entire study period. * Vaccination against influenza since January 2009 with a seasonal influenza vaccine. * Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to the administration of the study vaccine. * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination. * History of hypersensivity to a previous dose of influenza vaccine. * History of allergy or reactions likely to be exacerbated by any component of the vaccine(s). * Acute clinically significant pulmonary, cardiovascular, hepatic, renal, neurological and psychiatric disorders, as determined by clinical evaluation or pre-existing laboratory screening tests. * Acute disease and/or fever at the time of enrolment. * Fever is defined as temperature \>=37.5°C on oral setting. * Subjects with a minor illness without fever may be enrolled at the discretion of the investigator. * Administration of immunoglobulins and/or any blood products within the three months preceding the administration of the study vaccine or planned administration during the study. * Any medical conditions in which IM injections are contraindicated * Pregnant or lactating female. * Female planning to become pregnant or planning to discontinue contraceptive precautions.