The study will be conducted in 2 stages: a 3-dose primary vaccination at 2, 4 and 6 months of age and a booster vaccination at 12 to 15 months of age. All subjects will have 3 blood samples taken. Half of the subjects of each group will have a blood sample taken just prior to the administration of the third dose of the primary vaccination and the other half of the subjects of each group will have a blood sample taken at one month after the third vaccine dose of the primary vaccination phase. In addition, all subjects of all groups will have a blood sample taken before and 42 days after administration of the booster dose.