The purpose of this study is to assess the safety and the body's immune response to an experimental H1N1 influenza vaccine in healthy adult and elderly populations. The study will enroll up to 590 healthy adults ages 18 and older with no history of H1N1 infection or vaccination. 354 individuals will be 18-64 years old, and the other 236 will be greater than or equal to 65 years of age.