Blinding: In this randomized trial design, no attempt will be made to blind the infants being randomized, or their parents (in order to avoid unnecessary injections through a double dummy design). The investigator involved in randomizing the infants will also not be blinded. However, the laboratory personnel performing the antibody level measurements will be blinded by sending the samples with only a four digit code that does not reveal the intervention received.Samples during any visit will be withdrawn prior to administration of vaccine(s).