Phase IV Clinical Trial, Immunogenicity and Safety of EV71 Vaccine

Inclusion Criteria: * Healthy volunteers aged 6-35 months old * 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 * Proven legal identity Exclusion Criteria: For subjects with any of the following conditions, vaccination should not be administrated: * 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 * Severe chronic diseases * Thrombocytopenia or hemorrhagic disease * Immunodeficiency disease or receipt of immunosuppressant treatment * Uncontrolled epilepsy or progressive neurological disorders(e.g. Guillain-Barre syndrome) * Acute disease or acute stage of chronic disease prior to the study entry * History of thyroidectomy, thyroid disease within 12 months prior to the study entry * Asplenia or functional asplenia * Axillary temperature \>37.0 ℃ * Any other factor that suggesting the volunteer is unsuitable for this study based on the judgment of investigators Exclusion Criteria of the Second Injection: * Subjects with any of the following conditions are forbidden to continue the 2nd dose of vaccination: 1. Any serious adverse event that has a causal relationship with the investigated vaccine 2. Severe allergic reactions or hypersensitivity after vaccination (including urticaria / rash appear within 30 minutes after vaccination 3. Any confirmed or suspected autoimmune disease or immunodeficiency disease (e.g., HIV infection) 4. Other reactions (including severe pain, severe swelling, severe activity limitation, persistent hyperthermia, severe headache or other systemic or local reactions)determined by the investigators * For subjects suffering from acute disease or acute stage of chronic disease , whether to continue vaccination depends on themselves * Subjects with the following conditions may receive vaccination in delayed time or withdraw from the study depending on the judgment of investigator 1. Acute disease (moderate or severe disease with or without fever) in case of vaccination 2. Axillary temperature \> 37.0 °C