To evaluate the safety and immunogenicity of GSK Biologicals' live attenuated MMR vaccine (Priorix) in a local population in Singapore. The vaccine was administered as a single dose to healthy children (12-18 months of age) and blood samples were collected at two time points (before vaccination and after vaccination).

Inclusion Criteria:

• A male or female infant between 12 and 18 months of age at the time of the vaccination
• Written informed consent obtained from the parents or guardians of the subject.
• Free of obvious health problems as established by medical history and clinical examination before entering into the study.

Exclusion Criteria:

• Use of any investigational or non-registered drug or vaccine other than the study vaccine(s) during the study period or within 30 days preceding the dose of study vaccine
• Previous vaccination against mumps and/or rubella
• History of, or intercurrent, measles, mumps, and/or rubella disease
• Known exposure to measles, mumps or rubella within 30 days prior to the start of the study
• Any confirmed or suspected immunosuppressive or immunodeficient condition, including human immunodeficiency virus (HIV) infection.

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