Inclusion Criteria:

• Subjects who were previously vaccinated with GlaxoSmithKline Biologicals Fluarix™ or FluAS25 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.