 This study is an open-label, individual-randomized, parallel-group, comparative immunogenicity trial. Participating infants randomized to Group A will receive one dose each of measles vaccine MV, yellow fever vaccine YFV, and meningitis conjugate vaccine PsA-TT-5μg at 9 months of age, and infants randomized to Group B will receive one dose each of MV, YFV, PsA-TT-5μg, and PRV at 9 months of age. 