Study on Immunization Schedule of Beijing Tiantan Biological's Measles-mumps-rubella(MMR) Vaccine

Inclusion Criteria: * healthy children; 150 subjects 18 months old; 150 subjects 4 years old;300 subjects 5 years old; 150 subjects 6 years old; their guardians signed informed consent; * undiagnosed as measles, mumps and rubella; * in good health as determined by the outcome of medical history, physical examination and clinical judgment; suitable to MMR immunization; * guardians would comply with the requirements of the protocol; * immunized with MR or measles vaccine(MV) at 8 months old;immunized with MMR at 18 months old(not applicable to subjects 18 months old); unvaccinated by biological products within one month; * Axillary temperature ≤37℃; * the local household population or permanent population; Exclusion Criteria: * history of allergic disease or reactions likely to be exacerbated by any component of the vaccine(any previous vaccination history of allergies and egg allergy history); * Current confirmed as acute disease, severe chronic diseases or acute development of chronic diseases; * Participating in another clinical trial at the same time;