Study to Evaluate Immunological Equivalence Between Two Investigational Influenza Vaccines in Adults (H1N1)

The primary purpose of the study is to assess the equivalence of the immune response elicited by two GSK Biologicals' adjuvanted influenza investigational vaccines (GSK2340272A and GSK2340274A) in adults aged 18 to 60 years. The second purpose of the study is to evaluate the safety and reactogenicity of these two vaccines.

This Protocol Posting has been updated following Protocol Amendment 4, July 2010, leading to removal of one of the secondary outcome measures.

Eligibility Criteria:
Inclusion Criteria:

* Male or female aged 18 to 60 years inclusive, at the time of the first vaccination.
* Subjects who the investigator believes that they can and will comply with the requirements of the protocol.
* Written informed consent obtained from the subject.
* Satisfactory baseline medical assessment by history and physical examination.
* Access to a consistent means of telephone contact, which may be either in the home or at the workplace, land line or mobile, but NOT a pay phone or multiple-user device
* Females of non-childbearing potential may be enrolled in the study.
* Female of childbearing potential may be enrolled in the study, if she:
* 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 during the entire treatment period and for 2 months after completion of the vaccination series.

Exclusion Criteria:

* Use of any investigational or non-registered product other than the study vaccine within 30 days preceding the first dose of the study vaccine or planned use during the study period.
* Presence of evidence of substance abuse or of neurological or psychiatric diagnoses which, although stable, are deemed by the investigator to render the potential subject unable/unlikely to provide accurate safety reports.
* Presence of an axillary temperature \>= 37.5°C (99.5°F), or acute symptoms greater than "mild" severity on the scheduled date of first vaccination. NOTE: The subject may be vaccinated at a later date, provided symptoms have resolved, vaccination occurs within the window specified by the protocol, and all other eligibility criteria continue to be satisfied.
* Clinically or virologically confirmed influenza infection within 6 months preceding the study start.
* Diagnosed with cancer, or treatment for cancer, within 3 years.
* Any confirmed or suspected immunosuppressive or immunodeficient condition including history of human immunodeficiency virus (HIV) infection.
* Clinically or virologically confirmed influenza infection within 6 months preceding the study start.
* Chronic administration of immunosuppressants or other immune modifying drugs within 6 months of study enrolment or planned administration during the study period.
* Receipt of any immunoglobulins and/or any blood products within 3 months of study enrolment or planned administration of any of these products during the study period.
* Any significant disorder of coagulation or treatment with warfarin derivatives or heparin.
* An acute evolving neurological disorder or history of Guillain-Barré syndrome.
* Administration of any vaccines within 30 days before vaccination.
* Any known or suspected allergy to any constituent of influenza vaccines; a history of anaphylactic-type reaction to any constituent of influenza vaccines; or a history of severe adverse reaction to a previous influenza vaccine.
* Pregnant or lactating female
* Female planning to become pregnant or planning to discontinue contraceptive precautions.
* Any conditions which, in the opinion of the investigator, prevents the subjects from participating in the study.