Respiratory Syncytial Virus (RSV) Investigational Vaccine in Infants Aged 6 and 7 Months Likely to be Unexposed to RSV

The RSV PED-011 study was designed to evaluate the safety, reactogenicity and immunogenicity
of the RSV candidate vaccine when administered to infants aged 6 and 7 months before moving
to a proof-of-concept trial in infants. The ChAd155-RSV vaccine will be administered before
the RSV season to increase the probability of enrolling infants unexposed to RSV, who will be
followed through two RSV seasons. For the 2 dose groups, the second dose of ChAd155-RSV
vaccine will be given one month after the first dose. Approximately two thirds of the infants
(100) in this study will be given the ChAd155-RSV vaccine, whereas all infants (150) will
receive either an active control comparator vaccine (Bexsero, or Nimenrix, or Synflorix, or
Menveo), or Placebo (Formulation buffer S9b). After a screening visit lasting up to 30 days
(Epoch 1), this study will be conducted in an observer-blind manner, during the 2 month
vaccination phase (Epoch 2) and in a single-blinded manner during the follow-up phase, for 10
months until the end of the first RSV season (Epoch 3) and then for an additional follow-up
year, until the end of the second RSV season (Epoch 4).

Inclusion Criteria:

- Subjects' parent(s)/Legally Acceptable Representative [LAR(s)] who, in the opinion of
the investigator, can and will comply with the requirements of the protocol

- Written informed consent obtained from the parent(s)/LAR(s) of the subject prior to
performing any study specific procedure.

- A male or female between and including 6 and 7 months of age (from the day the infant
becomes 6 months of age until the day before the infant achieves 8 months of age) at
the time of the first vaccination.

- Healthy subjects as established by medical history and clinical examination before
entering into the study.

- Born full-term with a minimum birth weight of 2.5 kilograms (kg).

- Subjects' parent(s)/LAR(s) need to have access to a consistent mean of telephone
contact or computer.

Exclusion Criteria:

- Child in care

- Use of any investigational or non-registered product other than the study vaccine
during the period starting 30 days before the first dose of study vaccine (Day -29 to
Day 1), or planned use during the study period.

- Chronic administration of immunosuppressants or other immune-modifying drugs during
the period starting six months prior to the first vaccine. For corticosteroids, this
will mean prednisone ≥ 0.5 milligrams (mg)/kg/day (for pediatric subjects), or
equivalent. Topical steroids are allowed.

- Administration of long-acting immune-modifying drugs or planned administration at any
time during the study period.

- Administration of immunoglobulins and/or any blood products during the period starting
three months before the first dose of study vaccine or planned administration during
the study period.

- Planned administration/administration of a vaccine not foreseen by the study protocol
in the period starting 30 days before the first dose and ending 30 days after the last
dose of vaccine administration, with the exception of scheduled routine pediatric
vaccines. Scheduled routine pediatric vaccines may be administered ≥ 7 days before a
dose of study vaccine or ≥ 7 days following a dose of study vaccine, with the
exception of live viral vaccines which may be administered ≥ 14 days before a dose or
≥ 7 days after a dose.

- Acute or chronic, clinically significant pulmonary, cardiovascular, hepatic or renal
functional abnormality, as determined by physical examination or laboratory screening
tests.

- A history of, or on-going confirmed RSV disease or highly compatible clinical picture.

- Serious chronic illness.

- Major congenital defects.

- History of any neurological disorders or seizures.

- History of or current autoimmune disease.

- History of recurrent wheezing.

- History of chronic cough.

- Previous hospitalization for lower respiratory illnesses.

- Previous, current or planned administration of Synagis (palivizumab).

- Neurological complications following any prior vaccination.

- Born to a mother known or suspected to be Human Immunodeficiency Virus (HIV)-positive
.

- Any confirmed or suspected immunosuppressive or immunodeficient condition, based on
medical history and physical examination .

- Family history of congenital or hereditary immunodeficiency.

- Previous vaccination with a recombinant simian or human adenoviral vaccine.

- History of any reaction or hypersensitivity likely to be exacerbated by any component
of the vaccine.

- Hypersensitivity to latex.

- Current severe eczema.

- Acute disease and/or fever at the time of enrolment (Visit 1).

- Any clinically significant Grade 1 or any ≥ Grade 2 hematological or biochemical
laboratory abnormality detected at the last screening blood sampling.

- Any medical condition that in the judgment of the investigator would make
intramuscular (IM) injection unsafe.

- Any other conditions that the investigator judges may interfere with study procedures,
findings.

- Any conditions that could constitute a risk for the subjects while participating to
this study.

- Weight below the fifth percentile of the local weight-for-age curve.

- Concurrently participating in another clinical study, at any time during the study
period, in which the subject or mother has been or will be exposed to an
investigational or a non-investigational vaccine/product.

- Planned move to a location that will prohibit participating in the trial until study
end.

- For Thailand only, subjects who have received Synflorix prior to enrolment.