Evaluating the Infectivity, Safety and Immunogenicity of a Recombinant Live-Attenuated Respiratory Syncytial Virus Vaccine (RSV LID cp ΔM2-2) in RSV-Seronegative Infants 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
evaluated the safety, infectivity, and immunogenicity of a single dose of RSV LID cp ΔM2-2, a
recombinant live-attenuated RSV vaccine, in RSV-seronegative infants 6 to 24 months of age.

Participants were randomly assigned to receive a single dose of the RSV LID cp ΔM2-2 vaccine
or placebo at study entry (Day 0).

Participants were enrolled in the study between April 1 and October 14 (outside of RSV
season) and remained on study until they completed the post-RSV season visit between April 1
and April 30 in the calendar year following enrollment. Participants' total study duration
was between 6 and 10 months, depending on when they enrolled in the study. Participants
attended several study visits throughout the study, which may include physical examinations,
blood collection, and nasal washes. Participants' parents or guardians were contacted by
study staff at various times during the study to monitor participants' health.

The study was closed to accrual early after interim data were reviewed by a subset of
protocol team members and it was concluded that this vaccine candidate will not meet the
criteria listed in the protocol for a good vaccine candidate. This recommendation was shared
with the (blinded) protocol chair and the Medical Officers, as well as the Data Safety and
Monitoring Board (DSMB), who agreed with the unblinded protocol team members' assessment. The
targeted sample size was 33 (22 in the vaccine arm and 11 in the placebo arm). Participants
already on study at the time of the early closing decision remained on study and completed
the follow-up per protocol.

Inclusion Criteria:

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

- Good health based on review of the medical record, history, and physical examination,
without evidence of chronic disease.

- Parents/guardians willing and able to provide written informed consent as described in
the protocol.

- 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. Note: results from specimens collected during screening for IMPAACT 2011
were acceptable as long as within the 42-day window.

- Growing at a normal velocity for age (as demonstrated on a standard growth chart) AND

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

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

- Received routine immunizations appropriate for age (as per national Center for Disease
Control Advisory Committee on Immunization Practices [ACIP]).

- Expected to be available for the duration of the study.

- If born to an HIV-infected woman, participant must not have been breastfed and must
have had documentation of 2 negative HIV nucleic acid (RNA or DNA) test results from
samples collected on different dates with both collected when greater than or equal to
1 month of age and at least one collected when greater than or equal to 4 months of
age, and no positive HIV nucleic acid (RNA or DNA) test; or 2 negative HIV antibody
tests, both from samples collected at greater than or equal to 6 months of age.

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 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 were allowed to enroll.

- 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 enrolled, or scheduled to be
enrolled in IMPAACT 2011, 2012 or 2013 AND 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 greater than or equal to 6 years of age with HIV-related
immunodeficiency, defined as having a most recent CD4 T lymphocyte cell count
less than 300 cells/mm^3. CD4 T lymphocyte count must have been measured within 6
months prior to enrollment, or

- a person age 1 year up to less than 6 years with HIV-related immunodeficiency,
defined as having a most recent CD4 T lymphocyte cell percentage less than 25 or
CD4 T lymphocyte count less than 750 cells/mm^3 (if both values available, use
the lower of the two). CD4 T lymphocyte parameter must have been measured within
the 6 months prior to enrollment; or

- a person age less than 1 year with HIV-related immunodeficiency, defined as
having a most recent CD4 T lymphocyte cell percentage less than 30 or CD4 T
lymphocyte count less than 1000 cells/mm^3 (if both values available, use the
lower of the two). CD4 T lymphocyte parameter must have been measured within the
6 months prior to enrollment; or

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

- a person receiving immunosuppressant agents; or

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

Verbal report of CD4 T cell lymphocyte is sufficient documentation if the parent/guardian
is confident of history.

- 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 (rectal temperature of greater than or equal to 100.4°F (38°C)), 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

Permitted concomitant medications (prescription or non-prescription) include nutritional
supplements, medications for gastroesophageal reflux, eye drops, and topical medications,
including (but not limited to) cutaneous (topical) steroids, topical antibiotics, and
topical antifungal agents.

- Receipt of salicylate (aspirin) or salicylate-containing products within the 28 days
prior to enrollment.

- 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.