This is a Phase 4, single-center, study of the immune responses of adults to one of two licensed influenza vaccines (either inactivated vaccine given IM or live, attenuated vaccine given intranasally). The study will enroll up to 60 adults, ages 18-49, some of whom were immunized in the Years 1 and 2 studies. This study began Year 1 of this grant with a protocol testing the two vaccine products in their age-approved populations. FluMist is approved for use in healthy children and adolescents, 5-17 years of age, and healthy adults 18-49 years of age. Fluzone is approved for all age groups starting at 6 months of age. To match for age and to study the youngest children possible, the age cohorts of 5-9 and 18-49 years were chosen for initial Year 1 study. In 2003, 70 adults and 16 children were enrolled, randomized 1:1 to receive either FluMist or Fluzone and immunized. In 2004, 44 of the original 70 adults were re-immunized with the same preparation they received in 2003. In addition, studies were conducted in twenty-eight 6mos to 5yo children who all received Fluzone and in thirty-nine 5-9 yo children who were randomized 1:1 to receive either FluMist or Fluzone. For 2005, we propose to study in this protocol, adults from last year who agree to a third immunization plus as many new adults to add up to a total of 60. Blood samples will also be taken at Days 0, 7-9 and 28 to be analyzed for CD4 and CD8 T-cell, B-cell, NK-cell and homing receptor responses.