- 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.