Immunogenicity and Safety Study of GlaxoSmithKline (GSK) Biologicals' Combined Measles-mumps-rubella (MMR) Vaccine in Subjects Four to Six Years of Age

The GSK Biologicals' MMR vaccine (Priorix®) and Merck's MMR vaccine (M-M-R®II) are referred
to as Inv_MMR vaccine and Com_MMR vaccine respectively. 2 lots of the comparator vaccine
(Com_MMR_L1 and Com_MMR_L2) will be used, but the 2 lots will be analysed as a pool.

The Inv_MMR vaccine will be administered as a second dose to children who already received a
first dose Com_MMR vaccine. Since the second dose of a MMR vaccine in the US is routinely
co-administered with DTaP-IPV vaccine (Kinrix®) and varicella vaccine (VV) (ProQuad® or
Varivax®), some children will receive one dose of these vaccines along with either of the MMR
vaccines.

Inclusion Criteria:

- Subjects who the investigator believes that they and/or their parent(s) or LAR/s can
and will comply with the requirements of the protocol.

- Male or female subjects 4 to 6 years of age at the time of vaccination.

- Written informed consent is obtained from the parent(s)/LAR(s) of the subject (assent
will be obtained from subjects in line with local rules and regulations).

- Subjects in stable health as determined by investigator's physical examination and
assessment of subjects' medical history.

- Subjects received either a single dose of M-M-R II, M-M-R VaxPro or ProQuad in the
second year of life.

- For subjects enrolled in the sub-cohort receiving co-administered DTaP-IPV and VV:

- subjects received previous DTaP vaccine doses with INFANRIX® and/or PEDIARIX® for
the first three doses and INFANRIX® for the fourth dose of the DTaP-containing
vaccine.

- subjects received a first dose of VV in the second year of life.

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 day of study vaccination/s or planned
during the entire study period.

- Previous vaccination with a second dose of measles, mumps, rubella containing
vaccine/s.

- Chronic administration of immunosuppressants or other immune-modifying drugs during
the period starting 180 days prior to Day 0 or any planned administration of
immunosuppressive and immune-modifying drugs during the entire study. Inhaled and
topical steroids are allowed.

- Administration of immunoglobulins and/or any blood products during the period starting
180 days before entering the study or planned administration from the date of
vaccination through the immunogenicity evaluation at Visit 2.

- Planned administration/ administration of a vaccine not foreseen by the study protocol
during the period starting 30 days prior to the study vaccination/s and ending 42 days
after the vaccination/s (at Visit 2), with the exception of live intranasal or
inactivated influenza (flu) vaccine, which may be given at any time during the study,
including the day of study vaccination/s. Inactivated influenza vaccine must be
administered at a different location from the study vaccine. Any age appropriate
vaccine may be given starting at Visit 2, and anytime thereafter.

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

- History of measles, mumps, and/or rubella disease.

- Known exposure to measles, mumps and/or rubella during the period starting 30 days
prior to enrollment.

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

- History of allergic disease or reactions likely to be exacerbated by any component of
the vaccine(s), including systemic hypersensitivity to neomycin or gelatin.

- Blood dyscrasias, leukemia, lymphomas of any type, or other malignant neoplasms
affecting the bone marrow or lymphatic systems.

- Acute disease at the time of enrollment. Acute disease is defined as the presence of a
moderate or severe illness with or without fever. Fever is defined as temperature
≥38°C (100.4°F) measured by any age appropriate route. All vaccines can be
administered to persons with a minor illness such as diarrhea, mild upper respiratory
infection without fever.

- Active untreated tuberculosis according to the subject's medical history.

- Any other condition which, in the opinion of the investigator, prevents the subject
from participating in the study.

In addition, for subjects enrolled in the sub-cohort receiving co-administered DTaP-IPV+VV:

- Previous vaccination with a second dose of varicella-containing vaccine.

- Receipt of any varicella-containing vaccine during the period starting 90 days before
the day of study vaccination.

- History of varicella/zoster disease.

- Known exposure to varicella/zoster during the period starting 30 days prior to
enrollment.

- History of diphtheria, tetanus, pertussis, and/or poliomyelitis disease.

- Vaccination against diphtheria, tetanus, pertussis or polio given after the second
year of life.

- Occurrence of transient thrombocytopenia or neurological complications following an
earlier immunization against diphtheria and/or tetanus toxoids.

- Following a previous administration of DTP vaccine: temperature ≥40.6°C (>105°F)
during the period starting 48 hours not due to another identifiable cause, collapse or
shock-like state during the period starting 48 hours, persistent, inconsolable crying
lasting three hours or more within 48 hours, seizures with or without fever occurring
during the period starting three days, or encephalopathy of unknown aetiology
occurring during the period starting 7 days of a previous administration of DTP
vaccine.

- Hypersensitivity reaction to any component of the DTaP-IPV and/or varicella vaccines.