Safety and Immunogenicity Study of Live Attenuated Mumps Vaccines in Healthy Infants

Inclusion Criteria: * Healthy volunteer between 8 - 18 months old; * Proven legal identity; * Guardian(s) of the volunteer should be capable of understanding the written consent form, and such form should be signed before the infant being included into this study; * Complying with the requirement of the study protocol; Exclusion Criteria: * Axillaty temperature \> 37.0 °C; * Any significant abnormity of heart, lung, liver, spleen, lymph nodes, or pharynx; * Acute disease or acute stage of chronic disease within 7 days prior to study entry; * Prior vaccination with mumps vaccine or with history of mumps infection; * History of allergy to any vaccine or vaccine ingredient, or serious adverse reaction(s) about vaccination, such as urticaria, difficulty in breathing, angioneurotic edema, abdominal pain, etc; * Receipt of any of the following products: 1. Any subunit vaccine or inactivated vaccine within 14 days prior to study entry; 2. Any live attenuated vaccine within 28 days prior to study entry; 3. Any other investigational medicine(s) within 30 days prior to study entry; 4. Blood product (e.g., immunoglobulin) within 3 months prior to study entry; 5. Any immunosuppressant, cytotoxic medicine, or inhaled corticosteroids (except corticosteroid spray for treatment of allergic rhinitis or corticosteroid treatment on surface for acute non-complicated dermatitis) within 6 month prior to study entry; * Epilepsy (except febrile seizures), history of seizures or convulsions, or a family history of mental illness; * Autoimmune disease or immunodeficiency; * Congenital malformation, developmental disorders, or serious chronic diseases (such as Down's syndrome, diabetes, sickle cell anemia or neurological disorders; * Severe malnutrition; * Diagnosed coagulation function abnormal (e.g., coagulation factor deficiency, coagulation disorder, or platelet abnormalities); * Any other factor that suggesting the volunteer is unsuitable for this study based on the opinions of investigators; * Participants with the following conditions between day 0 - 28 of this study would be included in the full analysis set (FAS), but would be excluded from the per protocol set (PPS): 1. Receipt of any other investigational or unregistered product (drug or vaccine); 2. Receipt of immunosuppressant (corticosteroid dosage that equivalent to or above 0.5 mg prednisone/kg weight/day) for \> 14 days consecutively, except for inhalant or locally administrated corticosteroid; 3. Receipt of immunoglobulin and/or blood product; 4. Newly diagnosed autoimmune disease or immunodeficiency (e.g., HIV infection);