 Patient participation in this study will be for at least 60 days, with patients followed for at least 42 days after vaccination. In this study, participants will be enrolled sequentially, from highest to lowest dose of vaccine, into one of three groups. At study entry at Day 0, participants will be admitted to the hospital in order to familiarize them with trial procedures. Blood and nasal wash samples will be collected prior to vaccination. On Day 2, participants will have a physical exam and will receive one dose of vaccine; the vaccine will be administered as nose drops. Participants will undergo directed physical examinations daily while they are in the hospital. Nasal washes will also be collected daily from the day of admission through the day prior to discharge to test for the presence of vaccine virus. Participants may be discharged from the hospital after 3 consecutive negative viral cultures, but not before Day 14. Additional blood collection will occur daily from Day 0 to Day 7 and again on Day 21. Participants will return for follow-up visits 28 to 32 days and 42 to 46 days after receiving the vaccine. Blood and nasal wash collection will occur at these 2 study visits, and participants will also have directed physical exams. 