Evaluating the Infectivity, Safety and Immunogenicity of a Recombinant Live-Attenuated Respiratory Syncytial Virus Vaccine, LID/ΔM2-2/1030s, in RSV-Seronegative Infants and Children 6 to 24 Months of Age

Inclusion Criteria: * ≥ 6 months of age and \<25 months of age at the time of inoculation * Screening and pre-inoculation serum specimens for respiratory syncytial virus (RSV)-neutralizing antibody are obtained no more than 42 days prior to inoculation * Seronegative for RSV antibody, defined as serum RSV-neutralizing antibody titer \<1:40 * In good health based on review of the medical record, history, and physical examination at the time of inoculation * Received routine immunizations appropriate for age based on the Advisory Committee on Immunization Practices (ACIP) Recommended Immunization Schedule for Children and Adolescents Aged 18 Years or Younger * Growing normally for age as demonstrated on a World Health Organization (WHO) growth chart, AND * If \< 1 year of age: has a current height and weight above the 5th percentile for age * If ≥ 1 year of age: has a current height and weight above the 3rd percentile for age * Expected to be available for the duration of the study * Parent/guardian is willing and able to provide written informed consent Exclusion Criteria: * ≤ 6 months of age and \> 25 months of age at the time of inoculation * Born at less than 34 weeks gestation * Born at less than 37 weeks gestation, and at the date of inoculation less than 1 year of age * Maternal history of a positive HIV test before or during pregnancy * Evidence of chronic disease * Known or suspected infection or impairment of immunological functions * Bone marrow/solid organ t…