A randomized, placebo-controlled, double-blind clinical trial is to evaluate the safety and immunogenicity of a new inactivated EV71 vaccine developed by Sinovac Biotech CO., LTD.

Inclusion Criteria:

1. Healthy males and females, aged from 6 months to 11 years old Health is determined by medical history, physical examination, laboratory examination and clinical judgment of the investigator
2. Provided legal identification for the sake of recruitment.
3. Subjects and/or parent(s)/legal guardian(s) are able to understand and sign informed consents.
4. Birth weight more than 2500 grams

Exclusion Criteria:

1. History of Hand-foot-mouth Disease
2. Subject that has allergic history of vaccine, or allergic to any ingredient of vaccine
3. Serious adverse reactions to vaccines such as anaphylaxis, hives, respiratory difficulty, angioedema, or abdominal pain
4. Congenital malformations or developmental disorders, genetic defects, or severe malnutrition
5. Epilepsy, seizures or convulsions history, or family history of mental illness
6. Autoimmune disease or immunodeficiency, or parents, brothers and sisters have autoimmune diseases or immunodeficiency
7. History of asthma, angioedema, diabetes or malignancy
8. History of thyroidectomy or thyroid disease that required medication within the past 12 months
9. Bleeding disorder diagnosed by a doctor (e.g. factor deficiency, coagulopathy, or platelet disorder requiring special precautions) or significant bruising or bleeding difficulties with IM injections or blood draws
10. Asplenia, functional asplenia or any condition resulting in the absence or removal the spleen
11. Acute illness or acute exacerbation of chronic disease within the past 7 days
12. Any history of immunosuppressive medications or cytotoxic medications or inhaled corticosteroids within the past six months (with the exception of corticosteroid nasal spray for allergic rhinitis or topical corticosteroids for an acute uncomplicated dermatitis)
13. History of any blood products within 3 months
14. Administration of any live attenuated vaccine within 28 days
15. Administration of subunit or inactivated vaccines ,e.g., pneumococcal vaccine, or allergy treatment within 14 days
16. Axillary temperature > 37.0 centigrade before vaccination
17. Abnormal laboratory parameters before vaccination
18. Any medical, psychiatric, social condition, occupational reason or other responsibility that, in the judgment of the investigator, is a contraindication to protocol participation or impairs a volunteer's ability to give informed consent