The purpose of this study is to assess the immunogenicity and safety of EV71 vaccine (Envacgen®) in Children Aged 6 to <10 Years compared to Children Aged 2 to <6 Years.

This is a prospective, open-label, multi-center, phase 3 study. Participants will receive the first IM injection of study vaccine on Day 1 and will receive a second dose 56 days later. The last study visit is on Day 237 when participants will be contacted via telephone to assess for adverse events .

Inclusion Criteria:

1. Healthy children aged 2 to <10 years as established by medical history and clinical examination.
2. Subject and/or the subject's parent/guardian is able to understand and sign the ICF.

Exclusion Criteria:

1. Has poor venous access.
2. 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.
3. Has had previously known exposure to EV71 or has received EV71 vaccine.
4. Has a history of herpangina or HFMD associated with enterovirus infection in the past 28 days before the date of planned study drug vaccination.
5. Has been diagnosed with a significant neurological, pulmonary, cardiovascular, hematological, hepatic, or renal disorder.
6. Has a history of hypersensitivity to vaccines, or a history of allergic disease or reactions likely to be exacerbated by any component or any residual trace components such as formaldehyde of the Envacgen® vaccine.
7. Has used any investigational/nonregistered product (including drug, vaccine, or invasive medical device) within 28 days before study vaccination or plans to use any of them during the study period.
8. Has confirmed or suspected autoimmune disorder or immunodeficiency.
9. Has been administered or plans to be administered with any licensed live attenuated vaccine within 14 days before or after each study vaccination.
10. Has used immunoglobulins via intravenous route or any blood products within 11 months before vaccination or plans to use any of them during the study period.
11. Has received immunosuppressant, cytotoxic drug, corticosteroid (including prednisolone ≥ 0.5 mg/kg/day or equivalent), immunomodulator or acetylsalicylic acid for > 14 days within 6 months before the first vaccination or plans to use any of them during the study period. (Inhaled and topical steroids are allowed).
12. Has any medical or psychiatric condition that is a contraindication to protocol participation based on the judgment of the Investigator.