A Study to Evaluate the Efficacy, Safety, and Immunogenicity of an EV71 Vaccine

Inclusion criteria

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

Exclusion criteria

• Age < 2 months or ≥ 6 years.
• For subjects < 1 year, gestational age < 34 weeks or birth weight < 2200 grams.
• Has poor venous access (for subjects in sub-study only).
• 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.
• Has had previous known exposure to EV71 or has received EV71 vaccine.
• 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.
• Has been diagnosed with a significant neurological, pulmonary, cardiovascular, hematological, hepatic, or renal disorder.
• 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.
• Has used any investigational/non-registered product (including drug, vaccine, or invasive medical device) within 28 days before vaccination or plan to use during the study period.
• Has confirmed or suspected autoimmune disorder, or immunodeficiency.
• Administration of any licensed live attenuated vaccine within 14 days before or after each study vaccination (with the exceptions of live attenuated Rotavirus vaccine via oral route).
• Has used immunoglobulins or any blood products within 11 months before vaccination or plan to use during the whole study period.
• 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).
• Has any medical or psychiatric condition, that is a contraindication to protocol participation based on the judgment of the Investigator.