This trial is a Phase IIIA, randomized, observer-blind, controlled, multi-center, multi-country study with four parallel groups. This study will evaluate the immunogenicity and safety of GSK Biologicals' trivalent investigational MMR vaccine (referred to as Inv_MMR vaccine, throughout this document) in contrast to the US standard of care comparator vaccine (M-M-R II, Merck and Co., Inc., referred to as Com_MMR throughout this document) in children during their second year of life. The first dose of this two-dose study is designed to establish the end of shelf-life potency of Inv_MMR vaccine. The Inv_MMR vaccine will be given as one of two lots; one of a minimum potency, designated Inv_MMR_Min; and the other at a mid-range or medium potency designated Inv_MMR_Med to two groups. The second dose for both of these Inv_MMR groups will have a potency within the release range of the marketed vaccine. The Com_MMR vaccine will consist of two lots designated Com_MMR_L1 and Com_MMR_L2 and will be analyzed as pooled lots within the study. The first MMR vaccine dose will be co-administered with Varivax, Havrix and (in the US sub-cohort only) Prevnar 13 which are routinely administered to children of this age in the US.
The purpose of this study is to evaluate end of shelf-life potency in terms of the immunogenicity and safety of GSK Biologicals' trivalent MMR vaccine, by comparing it to Merck & Co., Inc.'s MMR vaccine, which is approved for use in the United States (US).