Assess the immunological behavior of children from 2 months of age that receive one out of seven anti-rotavirus vaccination programs: Group 1 (routine schedule with two doses of RV1 - Rotarix plus sterile water) and Group 2 (routine schedule with three doses of RV5 - RotaTeq) versus Group 3 (one dose of monovalent vaccine followed by two doses of pentavalent vaccine), Group 4 (one dose of pentavalent vaccine followed by two doses of monovalent vaccine), Group 5 (two doses of pentavalent vaccine followed by a dose of monovalent vaccine), Group 6 (one dose of pentavalent vaccine followed by a dose of monovalent vaccine and a dose of pentavalent vaccine), and Group 7 (a dose of monovalent vaccine followed by a dose of pentavalent vaccine and a dose of monovalent vaccine) in children from Mexico City.