Phase 3 Study of BK1310 in Healthy Infants

Inclusion Criteria: * Healthy infants aged ≥2 and \<43 months at the first vaccination of the study drug (recommended: ≥2 and \<7 months). Those who are applicable of the following conditions must be carefully observed before the enrollment: infants with known underlying disease such as cardiovascular disease, renal disease, hepatic disease, blood dyscrasia, respiratory disease or developmental disorder. Infants who developed fever within 2 days after any previous vaccination. Infants with history of convulsions. * Written informed consent is obtained from a legal guardian (parent) Exclusion Criteria: * With past diagnosis of immunodeficiency or currently under immunosuppressive treatment * Have close relatives (the third degree of kinship) diagnosed with congenital immunodeficiency * Possibility of anaphylaxis due to food or pharmaceuticals * With experience of Hib infection, diphtheria, pertussis, tetanus or acute poliomyelitis * With experience of Hib, diphteria, pertussis, tetanus or polio vaccination. * Administered a live vaccine within 27 days before the first vaccination of the study drug, or inactivated vaccine or toxoid within 6 days before vaccination * Administered transfusion, immunosuppressant (excluding drugs for external use), or immunoglobulin formulation * Administered corticosteroid 2 mg/kg per day or more as prednisolone (excluding drugs for external use) * Participated in other studies within 12 weeks before obtaining consent * With the gestational age \<37 weeks or weighed less than 2500 grams at birth. * Considered to be not eligible by the principal investigators (sub-investigators) of the enrollment.