This is a study to evaluate the immunogenicity and safety of GlaxoSmithKline (GSK) Biologicals combined measles-mumps-rubella varicella candidate vaccine given to healthy children in their second year of life.

Separate injections of the licensed Priorix (MMR vaccine) and Varilrix (chickenpox vaccine) serve as control.

Inclusion Criteria:

• A male or female subject between 11-13 months of age (i.e. from 11 month birthday until the day before the 14 month birthday) at the time of the first vaccination.

Exclusion Criteria:

• History of previous measles, mumps, rubella and/or varicella vaccination or disease, or known exposure to any of these diseases within 30 days prior to the start of the trial
• Planned administration of a vaccine not foreseen by the study protocol from 30 days prior to each vaccination until 42-56 days after each vaccination

Patient-level data for this study will be made available through www.clinicalstudydatarequest.com following the timelines and process described on this site.