This was a Phase II prospective, single-blind to dose, randomized study that compared the immunogenicity of subjects receiving half-dose Fluzone® compared to full-dose Fluzone®, 2004-2005 formulation. 1440 healthy subjects, ages 18-64 years old and not currently indicated for influenza vaccination under the interim ACIP guidelines, were stratified by age, gender, and previous exposure to influenza vaccine, and randomized to receive either half-dose Fluzone® or full-dose Fluzone®.