The Phase IVd of Inactivated Enterovirus 71 Vaccine

Inclusion Criteria: * Healthy subjects (6-71 months old children) as established by medical history and clinical examination * The subjects' legal guardian must be aware of this vaccines * The subjects' legal guardian voluntarily participate in the study and signed Informed Consent Form * Subjects with temperature ≤ 37.0 ℃ * The subjects' legal guardian with the ability and objective to comply with the requirements of the protocol * Persist for a 14-month visit (and receive blood, stool (or specimens by means of a swab) tests according to program requirements in immunogenicity observation group) Exclusion Criteria: * Allergy or serious side-effects to a vaccine or any ingredient of vaccine * Epilepsy, seizures, convulsions, neurological illness * Congenital or hereditary immunodeficiency * Autoimmune disease * Asthma, thyroidectomy, angioneurotic edema, diabetes or cancer * Asplenia, functional asplenia, and any circumstances leading to the asplenia or splenectomy * Clinical diagnosis of coagulopathy (such as clotting factor deficiency, coagulation disorders, platelet abnormalities), significant bruising or blood clotting disorder * Acute illness or acute exacerbation of chronic disease in last 7 days * Any prior administration of immunodepressant or corticosteroids in last 6 months * Any prior administration of blood products in last 3 months * Any prior administration of live-attenuated vaccine in last 15 days * Any prior administration of subunit or inactivated vaccines in last 7 days * Fever before vaccination, axillary temperature ﹥37.0 ℃ * The laboratory test abnormalities before vaccination, including blood tests (hemoglobin, total white blood cells, WBC, platelets), blood biochemistry tests (ALT, total bilirubin, direct bilirubin, Cr, BUN) and urine tests (urine protein, urine sugar, blood cells), etc. * Hypertension or hypotension. Systolic blood pressure ﹥140 mmHg and/ or diastolic blood pressure ﹥90 mmHg; systolic blood pressure ﹤90 mmHg and/or diastolic blood pressure ﹤60 mmHg * Any condition that in the opinion of the investigator, may interfere with the evaluation of study objectives * take part into other vaccine or drug clinical trials in last half year