A Study of BLB-201 RSV Vaccine in Infants and Children

Inclusion criteria for sero+ children 18 to 59 months of age enrolled in Groups 1 and 2: Healthy children at least 18 months but less than 60 months of age whose legally-acceptable representative (LAR) understands and signs the trial informed consent and agrees to vaccine administration following a detailed explanation of the trial. Determined by medical history, targeted physical exam, and clinical judgement of the investigator to be in a good state of health. Screening laboratory values slightly outside lab normal ranges may be acceptable if the site investigator determines that they are not clinically significant. Permitted concomitant medications include nutritional supplements, medications for gastroesophageal reflux, eye drops, and topical medications, including topical steroids, topical antibiotics, and topical antifungal agents. Sero+ for RSV as defined by serum RSV antibody titer assay Participant is expected to be available for the duration of the trial. The LAR confirms that the subject has received routine immunizations appropriate for age based on the current 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 has a current height and weight above the 3rd percentile for age. Inclusion criteria for sero+ or sero- infants and children 8 to 24 months of age enrolled in Groups 3 through 6: Healthy children at least 8 months but less than 25 months of age whose LAR understands and signs the trial informed consent and agrees to vaccine administration following a detailed explanation of the trial. Determined by medical history, targeted physical exam, and clinical judgement of the investigator to be in a good state of health. Screening laboratory values slightly outside lab normal ranges may be acceptable if the site investigator determines that they are not clinically significant. Permitted concomitant medications include nutritional supplements, medications for gastroesophageal reflux, eye drops, and topical medications, including topical steroids, topical antibiotics, and topical antifungal agents. Sero- OR sero+ for RSV antibody, defined by serum RSV antibody titer assay not more than 30 days prior to vaccination. Participant is expected to be available for the duration of the trial. The LAR confirms that subject has received routine immunizations appropriate for age based on the current 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. Subject Exclusion Criteria \<8 months of age and \>60 months of age at the time of planned vaccine inoculation. Born at less than 34 weeks gestation for subjects ≥ 1 year of age at enrollment 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. Maternal history of illicit drug abuse or alcohol abuse. Evidence of chronic disease except for chronic diseases that are mild, stable and not immune compromising or require recent change (\< 60 days) in management (e.g., mild stable eczema, mild allergic rhinitis) Clinically significant pulmonary, cardiovascular, hepatic or renal functional abnormality as determined by medical history or physical exam. Abnormal pulse oximetry testing during screening for undetected critical congenital heart disease or concern for such by medical history or physical exam. Acute or chronic medical condition or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgement, make the participant inappropriate for the study. History of severe infection (e.g., requiring hospitalization). Known or suspected impairment of immunological functions, bone marrow/solid organ transplant recipients. Receiving immunosuppressive therapy including systemic corticosteroids. Major congenital malformations, including congenital cleft palate or cytogenetic abnormalities. Suspected or documented developmental disorder, delay, or other developmental problem. Cardiac abnormality requiring treatment. Participants with clinically insignificant cardiac abnormalities (e.g., clinically insignificant patent foramen ovale) requiring no treatment may be enrolled. Lung disease or reactive airway disease. History of wheezing episode/s or receipt of bronchodilator therapy Previous receipt of supplemental oxygen therapy in a home setting. History of severe RSV infection or severe respiratory virus infection (e.g., requiring hospitalization). Previous immunization with an investigational RSV vaccine. Previous or planned administration of any anti-RSV antibody product within 6 months of receipt of study vaccine. Previous receipt of immunoglobulin or any other antibody products within the past 6 months. Previous receipt of any blood products within the past 6 months. Previous anaphylactic reaction. Previous serious vaccine-associated adverse reaction or one that was Grade 3 or above. Known hypersensitivity to any study vaccine product component. Household contact with any of the following groups of individuals for the period up to 28 days after vaccination (including after each dose for cohorts receiving two doses of vaccine): Member of a household that contains an infant who is less than 6 months of age at the date of inoculation through the 28th day after inoculation. In groups assigned to two doses of vaccine, to include date of inoculation through the 28th day after the second inoculation. Pregnant woman. Persons with hospitali