The study consists of four groups of children recruited in different centers in Finland. One group of children will receive the existing formulation of HRV vaccine and one group will receive the new formulation of the HRV vaccine. The other two groups will receive the placebo for existing formulation or the new formulation based on the allocation. The vaccine or placebo will be administered starting at 6 - 12 weeks of age according to 0, 1 month schedule. Routine childhood vaccinations are allowed according to local practice, but at least 14 days apart from each dose of study vaccine. The duration of the study will be approximately 2 months per child.