The purpose of this study is to evaluate the immunogenicity, safety and reactogenicity of one dose of four different formulations of the MenACWY conjugate vaccine when given to healthy children aged 12 14 months and 3 5 years. The selection of the best formulation will be based on data obtained up to one month after the vaccine dose. The Protocol Posting has been updated in order to comply with the FDA Amendment Act, September 2007.