Infectivity, Safety and Immunogenicity of a Recombinant Live-Attenuated Respiratory Syncytial Virus Vaccine (D46/NS2/N/ΔM2-2-HindIII) in RSV-Seronegative Infants and Children 6 to 24 Months of Age

Human respiratory syncytial virus (RSV) is the most common viral cause of serious acute lower
respiratory illness (LRI) in infants and children under 5 years of age worldwide. This study
will evaluate whether D46/NS2/N/ΔM2-2-HindIII vaccine is attenuated and immunogenic in
children 6 to 24 months of age.

Participants will be randomly assigned to receive a single dose of the RSV
D46/NS2/N/ΔM2-2-HindIII vaccine or placebo at study entry (Day 0).

Participants will be enrolled in the study between April 1 and October 31 (outside of RSV
season) and will remain on study until they complete the post-RSV season visit between April
1 and April 30 in the calendar year following enrollment. Participants' total study duration
will be between 6 and 13 months, depending on when they enroll in the study. Participants
will be evaluated in study visits that may include physical examinations, blood collection,
and nasal washes. Additionally, participants' parents or guardians will be contacted by study
staff at various times during the study to monitor participants' health.

Inclusion Criteria:

- Greater than or equal to 6 months (greater than or equal to 180 days) of age at the
time of screening and less than 25 months (less than 750 days) of age

- Participant is in good health based on review of the medical record, history, and
physical examination, without evidence of chronic disease

- Parents/guardians are willing and able to provide written informed consent

- Seronegative for RSV antibody, defined as a serum RSV-neutralizing antibody titer less
than 1:40 at screening from a sample collected no more than 42 days prior to
inoculation

- Is growing at a normal velocity for age as demonstrated on a standard growth chart AND

- If less than 1 year of age: has a current height and weight above the 5th
percentile

- If 1 year of age or older: has a current height and weight above the 3rd
percentile for age

- Participant has received routine immunizations appropriate for age (as per Center for
Disease Control Advisory Committee on Immunization Practices [ACIP])

- Participant is expected to be available for the duration of the study

Exclusion Criteria:

- Known or suspected HIV infection or impairment of immunological functions

- Receipt of immunosuppressive therapy, including any systemic, including either nasal
or inhaled, corticosteroids within 28 days of enrollment. Note: Cutaneous (topical)
steroid treatment is not an exclusion.

- Bone marrow/solid organ transplant recipient

- Major congenital malformations (such as congenital cleft palate) or cytogenetic
abnormalities

- Previous receipt of a licensed or investigational RSV vaccine or receipt of placebo in
any IMPAACT RSV study or previous receipt of or planned administration of any anti-RSV
product (such as ribavirin or RSV Ig or RSV mAb)

- Previous anaphylactic reaction

- Previous vaccine-associated adverse reaction that was Grade 3 or above

- Known hypersensitivity to any study product component

- Heart disease. Note: Participants with cardiac abnormalities documented to be
clinically insignificant and requiring no treatment may be enrolled

- Lung disease, including any history of reactive airway disease or medically documented
wheezing

- Member of a household that contains, or will contain, an infant who is less than 6
months of age at the enrollment date through Day 28

- Member of a household that contains another child who is, or is scheduled to be,
enrolled in CIR 311, 312 or 313 AND there has been or will be an overlap in residency
during that other child's participation in the study's Acute Phase (Days 0 to 28)

- Member of a household that contains an immunocompromised individual, including but not
limited to:

- a person who is HIV infected

- a person who has received chemotherapy within the 12 months prior to enrollment

- a person receiving immunosuppressant agents

- a person living with a solid organ or bone marrow transplant

- Attends a daycare facility and shares a room with infants less than 6 months of age,
and parent/guardian is unable or unwilling to suspend daycare for 28 days following
inoculation

- Any of the following events at the time of enrollment:

- fever (temporal or rectal temperature of greater than or equal to 100.4°F), or

- upper respiratory signs or symptoms (rhinorrhea, cough, or pharyngitis) or

- nasal congestion significant enough to interfere with successful inoculation, or

- otitis media

- Receipt of the following prior to enrollment:

- any killed vaccine or live-attenuated rotavirus vaccine within the 14 days prior,
or

- any live vaccine, other than rotavirus vaccine, within the 28 days prior, or

- another investigational vaccine or investigational drug within 28 days prior

- Scheduled administration of the following after planned inoculation:

- killed vaccine or live-attenuated rotavirus vaccine within the 14 days after, or

- any live vaccine other than rotavirus in the 28 days after, or

- another investigational vaccine or investigational drug in the 56 days after

- Receipt of immunoglobulin, any antibody products, or any blood products within the
past 6 months

- Receipt of any of the following medications within 3 days of study enrollment:

- systemic antibacterial, antiviral, antifungal, anti-parasitic, or antituberculous
agents, whether for treatment or prophylaxis, or

- intranasal medications, or

- other prescription medication except as listed below

- Receipt of salicylate (aspirin) or salicylate-containing products within the past 28
days

- Born at less than 34 weeks gestation

- Born at less than 37 weeks gestation and less than 1 year of age at the time of
enrollment

- Suspected or documented developmental disorder, delay, or other developmental problem

- Previous receipt of supplemental oxygen therapy in a home setting