Immunogenicity and Safety of Two Different Commercial EV71 Vaccines

Inclusion Criteria: * Healthy volunteer aged 6-35 months; * Proven legal identity; * Guardians of the participants should be capable of understanding the written consent form, and such form should be signed before the infant being included into this study. Exclusion Criteria: * Prior vaccination with EV71 vaccine; * History of hand，foot and mouth disease; * Allergy to gentamicin; history of allergy to any vaccine or vaccine ingredient, or serious adverse reaction(s) to vaccination, such as urticaria,difficulty in breathing, angioneurotic edema, pain, etc; * Congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc; * Autoimmune diseases or immunodeficiency/immunosuppression; * Severe neurological disorders (epilepsy, convulsions or convulsions) or psychosis; * History of thyroidectomy, absence of spleen, functional absence of spleen, and any circumstances leading to absence of spleen or splenectomy; * Diagnosed coagulation function abnormal (e.g., coagulation factor deficiency, coagulation disorder, or platelet abnormalities) , or obvious bruising or coagulation disorders; * 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) in the past 6 months; * Receipt of any of the following products: 1. Blood product within 3 months prior to study entry; 2. Any live attenuated vaccine within 14 days prior to study entry; 3. Any subunit vaccine or inactivated vaccine within 7 days prior to study entry; 4. Any other study drugs within 30 days prior to study entry; * Acute disease or acute stage of chronic disease within 7 days prior to study entry; * Axillary temperature \> 37.0℃; * Any other factor that suggesting the volunteer is unsuitable for this study based on the opinions of investigators.