As a result of the recent supply shortages in the U.S., as well as an anticipated increase in demand during the coming years, GSK Biologicals is pursuing licensure of Fluarix in the U.S. under the accelerated approval process; marketing approval most likely will be granted before the start of this clinical trial. GSK proposes to support U.S. licensure of Fluarix with this confirmatory post-marketing study. The purpose of the study is to evaluate the efficacy of a single dose of Fluarix in preventing influenza in adults during the 2005/2006 Influenza season.

Inclusion Criteria:

• A male or female age between, and including, 18 and 64 years of age at the time of the vaccination.
• Written informed consent obtained from the subject.
• Availability to follow up by phone during the study period.
• Female subjects must be of non-childbearing potential, i.e. either surgically sterilized or one year post-menopausal. If subject is of childbearing potential, she must be abstinent or have used adequate contraceptive precautions for 30 days prior to vaccination. She must also have a negative pregnancy test at study entry and must agree to continue such precautions for two months after vaccination.

Exclusion Criteria:

• 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 including egg, chicken protein, formaldehyde, thimerosal, gentamicin sulfate or sodium deoxycholate.
• Acute disease at the time of enrollment. (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. Oral temperature < 37.5°C).
• Pregnancy
• Chronic disorders of the pulmonary or cardiovascular system, including asthma
• History of requiring regular medical follow-up or hospitalization during the preceding year because of chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (including immunosuppression caused by medications or by human immunodeficiency virus.

Patient-level data for this study will be made available through www.clinicalstudydatarequest.com following the timelines and process described on this site.