A Study to Evaluate the Safety and Immunogenicity of GSK Biologicals' Seasonal Influenza Vaccine in Adults

Inclusion Criteria: * 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 18 years or above at the time of the vaccination. * Written informed consent obtained from the subject. * Healthy subjects or with well-controlled chronic diseases as established by medical history and clinical examination 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 other than the study vaccine(s) within 30 days preceding the vaccination or planned use during the study period. * Chronic administration of immunosuppressants or other immune-modifying drugs within six months prior to the vaccine dose. * Administration of immunoglobulins and/or any blood products within the three months preceding the administration of the study vaccine or planned during the study. * Administration of an influenza vaccine within 6 months preceding the study start. * Administration of an influenza vaccine other than the study vaccine during the entire study * Clinically or virologically confirmed influenza infection within 6 months preceding the study start * History of allergic disease or reactions likely to be exacerbated by any component of the vaccine. * Acute disease at the time of enrolment. * Acute clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination or laboratory screening tests. * Not stabilized or clinically serious chronic underlying disease. * Lactating female. * History of chronic alcohol consumption and/or drug abuse. * Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination. * Any condition which, in the opinion of the investigator, prevents the subject from participation in the study.