Immunogenicity and Safety of Trivalent Recombinant Hemagglutinin Influenza Vaccine in Healthy Adults

Inclusion Criteria: * Medically stable adults, aged 18-49 years. * Provided informed consent prior to any study procedures. * Able to comply with all study procedures. * Available for follow-up for the duration of the influenza season. * Women of child-bearing potential had a negative urine pregnancy test at the time of randomization and were willing to use an adequate form of contraception during the course of the study. Exclusion Criteria: * Any history of immunodeficiency or treatment with immunosuppressive medications. (Use of inhaled steroids or of topical steroids was not considered immunosuppressive; receipt of systemic glucocorticosteroids was not allowed if daily intake was \>10 mg of prednisone or equivalent). * Presence of high-risk conditions or other characteristics considered to be indications for influenza vaccination, as defined by the Advisory Committee on Immunization Practices (ACIP). * Acute febrile illness (defined as having a temperature ≥100degreesF) or upper respiratory tract illness within 72 hours of vaccination. * Use of experimental vaccines or any influenza vaccine after May 31st 2004 for the 2005 Southern Hemisphere or 2004 to 2005 Northern hemisphere epidemic seasons. * Use of any experimental medication within 30 days prior to study vaccination * Women who were pregnant or breast-feeding. * Subjects with a history of Guillain-Barré syndrome. * Receipt of parenteral immunoglobulin within 30 days prior to study vaccination. * Any acute or chronic condition that, in the opinion of the investigator, would render vaccination unsafe or interfere with the evaluation of response.