Study of the Safety and Immunogenicity of an Intranasal Vaccine for Respiratory Syncytial Virus in Seropositive Children

A Randomized, Single-Blind, Placebo-Controlled, Dose-Escalation Phase 1b Study to Evaluate the Safety and Immunogenicity of an Intranasal Live Attenuated Respiratory Syncytial Virus (RSV) Vaccine in Seropositive Young Children

This study evaluates an investigational vaccine that is designed to protect humans against infection with respiratory syncytial virus (RSV) and is administered as drops in the nose. Specifically, the study analyzes the safety of, and the immune response to, the vaccine when administered to healthy children between the ages of 15 and 59 months who are seropositive to RSV.

Key Inclusion Criteria:

1. Children aged 15-59 months
2. Good health based on history, physical examination and medical record review, without evidence or suspicion of chronic disease
3. Seropositive to RSV, as defined by serum neutralizing antibody titer above the threshold described in the study Analytical Plan
4. Written informed consent provided by parent(s)/guardian(s)

Key Exclusion Criteria:

1. Known or suspected chronic illness, particularly cardiopulmonary (including asthma or reactive airways disease), metabolic, hepatic, renal, or infectious (including recurrent or chronic sinusitis)
2. Known or suspected immunodeficiency
3. Household or close contact with anyone ≤ 6 months of age or with immunocompromised individual(s)
4. Nasal obstruction (including due to anatomic/structural causes, acute or chronic rhinosinusitis, or other causes)
5. Receipt of immunoglobulins, monoclonal antibodies and/or any blood products, or ribavirin within 3 months prior to study inoculation, or planned during study period
6. Receipt of an investigational RSV vaccine at any time
7. Any other condition that, in the judgment of the investigator, would be a risk to participant's safety and/or may interfere with study procedures or interpretation of results