Study Comparing the Immune Response of Fluarix and Fluzone Influenza Vaccines

* Experimental design: multi-center, randomized (1:1), observer-blind, active-controlled study in 2 parallel groups with approximately: * Study vaccine: full dose of Fluarix by IM administration. * Control vaccine: full dose of Fluzone by IM administration. * Two scheduled visits per subject at days 0 (visit 1) and 21(visit 2) with blood sample collected at each visit to evaluate the immune response. There will be a final contact with each subject 6 months after vaccination for safety follow up and study conclusion. * Vaccination schedule: one IM injection at day 0. * Type of study: Self contained.