To avoid confusion, inconvenience and error, and to limit differences among participants, DTaP, Hib, PCV, and HepB (if appropriate) will be administered along with IPV on first 3 visits in both cohorts. Both schedules meet the parameters of Advisory Committee of Immunization Practices (ACIP) (minimum interval at least 4 weeks between doses and minimum age of 6 weeks of age) 2.