Evaluate Vaccine Against Chickenpox and a Combined Vaccine Against 4 Viral Childhood Diseases: Measles, Mumps, Rubella and Chickenpox

An observer-blind study to evaluate GlaxoSmithKline Biologicals' live attenuated varicella vaccine and GlaxoSmithKline Biologicals' combined measles-mumps-rubella-varicella vaccine in the prevention of varicella disease in children. The Protocol Posting has been updated in order to comply with the FDA Amendment Act, Sep 2007.

According to treatment group allocation, participants will receive study vaccines and be followed for antibody titres and occurrence of varicella disease.

This study is conducted in 2 phases. Phase A includes the vaccination period and an observation period for efficacy. The efficacy endpoints will be evaluated over at least two years after vaccination. During this period, the immunogenicity endpoints will be evaluated with respect to the immune response 43 days after vaccination and the persistence of antibodies over two years to varicella (for all subjects) and to measles, mumps and rubella (for a subset of subjects). Regarding the safety endpoints, SAEs (including any complicated varicella cases if observed) will be assessed for all subjects during the whole Phase A duration, whereas, solicited (local and general) and unsolicited adverse events will be assessed in a subset of subjects within a 43-day period after vaccination.

Phase B is an extension of Phase A. It is a long-term follow-up until Year 10 to examine the long-term efficacy of the study vaccines against clinical varicella disease as well as the long-term persistence of antibodies to varicella (for all subjects) and to measles, mumps and rubella (in a subset of subjects) after vaccination.

Eligibility Criteria:
Inclusion criteria:

* Subjects for whom the investigator believes that their parents/guardians can and will comply with the requirements of the protocol for the whole duration of the study.
* Male or female subject between 12 and 22 months of age at the time of the first vaccination.
* Subjects free of obvious health problems, as established by medical history and physical examination before entering the study.
* Written informed consent obtained from the parents/guardians of the subject after they have been informed on the risks and benefits of the study, in a language they clearly understand and before performance of any study procedure.
* Subjects whose parents/guardians have direct access to telephone/mobile phone.
* Subjects:

  1. with at least one sibling (with negative history of varicella disease/vaccination) at home, or
  2. attending day care center, or
  3. attending childminders, i.e. someone taking care of several children, or
  4. who are in contact for at least once a week with other children without a known positive history of varicella disease/vaccination, while playing in close physical contact for more than 5 minutes.

Exclusion criteria:

* Previous vaccination against measles, mumps, rubella and/or varicella.
* History of previous measles, mumps, rubella and/or varicella/ herpes zoster diseases.
* Known exposure to measles, mumps, rubella and/or varicella/herpes zoster within 30 days prior to the start of the study.
* Chronic administration (defined as more than 14 days) of immunosuppressants or other immune-modifying drugs within six months prior to the first vaccine dose.
* Administration of immunoglobulins and/or any blood products within three months prior to the first vaccine dose or planned administration during the study period.
* Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical.
* Family history of congenital or hereditary immunodeficiency.
* History of allergic diseases or reactions likely to be exacerbated by any component of the vaccines, including systemic allergy to egg proteins or neomycin.
* Major congenital defects or serious chronic illness.
* Residence in the same household as newborns (0-4 weeks of age), pregnant women who are varicella-susceptible, persons with a known immunodeficiency or any other persons at high risk for varicella.
* History of any neurologic disorders or seizures.
* Use of any investigational or non-registered product (drug/vaccine other than the study vaccines) within 14 days prior to vaccination and planned use during the study period.

Additional exclusion criteria for subjects included in the subset:

- Administration of a licensed vaccine within 14 days prior to vaccination and planned use until approximately 42 days after the last study vaccine dose (Day 84) with the exception of oral polio vaccine (OPV).