A Phase 1 Study of the Safety and Immunogenicity of the Recombinant Live-Attenuated Chimeric Bovine/Human Parainfluenza Type 3 Virus Vaccine, rB/HPIV3, Lot PIV3 #101A, Delivered as Nose Drops to Adults 18 to 49 Years of Age, HPIV3-Seropositive Children 15 to 59 Months of Age, and HPIV3-Seronegative Infants and Children 6 to 36 Months of Age

HPIV type 3 (HPIV3) ranks second only to respiratory syncytial virus as the most common cause of bronchiolitis and pneumonia in infants less than 6 months of age. HPIV3 can cause severe disease in the first 2 years of life and is responsible for 11% of hospitalizations for respiratory diseases in children. This study will evaluate the safety and immunogenicity of a live, chimeric bovine/human, attenuated intranasal HPIV3 vaccine, rB/HPIV3. This vaccine combines modified human HPIV3 with a related, modified cow virus, bovine parainfluenza type 3 virus (BPIV3). Vaccinations will be given as nose drops to healthy adults, children seropositive for HPIV3, and infants and children seronegative for HPIV3.

There are four groups in this study. Group 1 will consist of adults who will receive the higher dose of rB/HPIV3. Group 2 will consist of seropositive children who will be randomly assigned to receive the higher dose of rB/HPIV3 or placebo. Group 2 will not begin enrollment until the completion of Group 1 safety data review. Participants of both Groups 1 and 2 will be monitored for 10 days post vaccination for respiratory illness and for fever by self-reported temperature logs; these participants will be followed for a maximum of 28 days. Blood collection will occur at study entry and on Day 28; additional blood collection may occur up to 28 days prior to vaccination. Clinical assessments and nasal washes will occur at study entry and selected study visits. Group 1 participants will be contacted by phone on Day 180; Group 2 participants' parents or guardians will be contacted by phone on Days 1, 2, 8, 9, 11, and 180; study staff will ask about any illnesses or adverse events that may have occurred.

Groups 3 and 4 will consist of seronegative infants and children. Group 3 will not begin enrollment until the completion of Group 2 safety data review. Children in Group 3 will be randomly assigned to receive the lower dose of rB/HPIV3 or placebo. Group 4 will not begin enrollment until the completion of Group 3 safety data review. Children in Group 4 will be randomly assigned to receive the higher dose of rB/HPIV3 or placebo. Participants of both Groups 3 and 4 will be monitored closely for 28 days postvaccination for respiratory illness and for fever by self-reported temperature logs; these participants will be followed for a maximum of 56 days. Blood collection will occur at study entry and on Day 56. Clinical assessments and nasal washes will occur at study entry and most study visits. Participants' parents or guardians will be contacted by phone periodically post vaccination; study staff will ask about any illnesses or adverse events they may have observed in their infants or children.