Safety of and Immune Response to Recombinant Live-Attenuated Parainfluenza Type 1 Virus Vaccine

Human Parainfluenza Virus Type 1 (HPIV1) is a leading cause of viral respiratory infections in children, the elderly, and those with compromised immune systems. HPIV1 is also the leading cause of viral croup in children under 6 years old. The purpose of this study is to determine the safety of and immune response to a HPIV1 vaccine, rHPIVI1 84/del170/942A, in 2 groups of adults and then in children who have been previously exposed to HPIV1. Once the safety of this vaccine has been established in these groups, an additional 2 groups of infants and children who have not been previously exposed to HPIV1 will be vaccinated. Naïve infants and children are the most vulnerable to naturally circulating HPIV1 and are the target population of this vaccine.