Evaluate reactogenicity & immunogenicity of an influenza pandemic candidate vaccine (GSK1562902A) in primed adults

•Subjects who the investigator believes can and will comply with the requirements of the protocol should be enrolled in the study. •For previously primed subjects: participation in the primary study (NCT00309634). •For unprimed subjects: male or female between and including, 19 and 61 years of age at the time of the first vaccination. •Written informed consent obtained from the subject. •Healthy subjects 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.

•Use of any investigational or non-registered product (drug or vaccine) other than the study vaccine(s) within 30 days preceding the first dose of study vaccine, or planned use during the study period. •For unprimed subjects who did not participate in the primary study (NCT00309634): Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose. •Planned administration/ administration of a licenced vaccine not foreseen by the study protocol within 2 weeks (for inactivated vaccines) or 4 weeks (for live vaccines) of the first dose of vaccine(s). •Concurrently participating in another clinical study, at any time during the study period, in which the subject has been or will be exposed to an investigational or a non-investigational product (pharmaceutical product or device). •Applicable for control group only: previous vaccination with a pandemic candidate vaccine or a vaccine containing the investigational vaccine adjuvant. •History of hypersensitivity to vaccines. •Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination (no laboratory testing required). •History of allergic disease or reactions likely to be exacerbated by any component of the vaccine(s). •Major congenital defects or serious chronic illness. •History of any neurological disorders or seizures. •Acute disease at the time of enrolment. •Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality, as determined by physical examination or laboratory screening tests. •Serious chronic disease including any medically significant chronic pulmonary, cardiovascular, renal, neurological, psychiatric or metabolic disorder, as determined by medical history and physical examination. •Any condition which, in the opinion of the investigator, prevents the subject from participation in the study. •Lactating female. •History of chronic alcohol consumption and/or drug abuse