Enterovirus 71 Infection

Primary Objective The primary objective of the study is:  To evaluate the clinical efficacy of EV71vac against EV71-associated disease. Secondary Objective(s) The secondary objectives of the study are:  To evaluate the efficacy of EV71vac against EV71-associated hospitalization and deaths.  To evaluate the immunogenicity of EV71vac in terms of neutralizing antibody (NTAb) titers induced by EV71vac.  To evaluate the safety of EV71vac  To evaluate the potential of cross-reaction of EV71vac in infants and children.  To evaluate the long-term safety and immunogenicity of EV71vac.  To evaluate the lot-to-lot consistency of 3 different lots of vaccine.

EV71 Vaccine

腸病毒71型(EV71) B4 subgenotype

Sterile suspension

EV71 2.5 mcg total protein formulated with phosphate buffered saline-based AlPO4

Primary Outcome Measures :
Number of Laboratory Confirmed EV71-Associated Disease [ Time Frame: Approximately 14 months ]
The primary outcome is the number of Laboratory confirmed EV71-associated disease by viral isolation or CODEHOP assay.

1. Healthy children and infants aged from 2 months to less than 6 years as established
by medical history and clinical examination.
2. The subjects’ parents/guardians are able to understand and sign the ICF.

1. Age < 2 months or ≥ 6 years.
2. For subjects < 1 year, gestational age < 34 weeks or birth weight < 2200 grams.
3. Has poor venous access (for subjects in sub-study only).
4. Currently has a fever defined as ear/rectal temperature ≥ 38°C or axillary
temperature ≥ 37.5 °C within 2 days before the time of planned vaccination.
5. Has had previous known exposure to EV71 or has received EV71 vaccine.
6. Has a history of herpangina or HFMD associated with enterovirus infection in the
past 30 days before the date of the planned study drug vaccination.
7. Has been diagnosed with a significant neurological, pulmonary, cardiovascular,
hematological, hepatic, or renal disorder.
8. Has a history of hypersensitivity to vaccines, or a history of allergic disease or
reactions likely to be exacerbated by any component of the vaccine.
9. Has used any investigational/nonregistered product (including drug, vaccine, and
invasive medical device) within 30 days before study drug vaccination or plan to
use during the study period.
10. Has confirmed or suspected autoimmune disorder, or immunodeficiency.
11. Administration of any licensed live attenuated vaccine within 30 days before or
after each study vaccination (with the exceptions of live attenuated Rotavirus
vaccine via oral route).
12. Has used immunoglobulins or any blood products within 11 months before
vaccination or plan to use during the whole study period.
13. Has had immunosuppressants, cytotoxic drugs, corticosteroids (including
prednisolone ≥ 0.5 mg/kg/day or equivalent), or immunomodulators taken for >
14 days within 6 months before first vaccination or plan to use before the last
scheduled study visit. (Inhaled and topical steroids are allowed).
14. Has any medical or psychiatric condition, that is a contraindication to protocol
participation based on the judgment of the Investigator.