This is a Phase I clinical trial including 2 parts to evaluate the safety and immune response to RotaTeq™ /placebo in subjects of 65 to 80 years of age. In Part I, approximately 60 subjects in US will be randomly assigned to 1 of 2 treatment groups receiving 3 doses of RotaTeq™ or placebo. In Part II, approximately 200 subjects internationally will be randomly assigned to 1 of 3 treatment groups. Part II will start after Part I data analysis is reviewed and approved by the FDA/CBER, the Safety Evaluation Committee (SEC) and other regulatory agencies. Duration for the entire study will be approximately 4 years.