Systems Biology of Vaccination for EV71 Vaccine in Humans

Inclusion Criteria: * Healthy subjects aged from 2 to 5 years old as established by medical history and clinical examination * The pre-vaccination neutralizing antibody against EV71 \<1:8 which is determined by ELISA * The subjects' guardians are able to understand and sign the informed consent * Had never received the vaccine against EV71 * Subjects who can and will comply with the requirements of the protocol * Subjects with temperature \<37.1°C on axillary setting Exclusion Criteria: * Subject who has a medical history of HFMD * \<= 37 weeks gestation * Subjects with a birth weight \<2.5 kg * Subject that has a medical history of any of the following: allergic history, or allergic to any ingredient of vaccine * Family history of seizures or progressive neurological disease * Family history of congenital or hereditary immunodeficiency * Severe malnutrition or dysgenopathy * Major congenital defects or serious chronic illness, including perinatal brain damage * Autoimmune disease * Bleeding disorder diagnosed by a doctor or significant bruising or bleeding difficulties with IM injections or blood draws * Any acute infections in last 7 days * Any prior administration of immunodepressant or corticosteroids in last 6month * Any prior administration of blood products in last 3 month * Any prior administration of other research medicines in last 1month * Any prior administration of attenuated live vaccine in last 28 days * Any prior administration of inactivated vaccines in last 14 days, such as pneumococcal vaccine * Under the anti - TB prevention or therapy * Any condition that in the opinion of the investigator, may interfere with the evaluation of study objectives