The purpose of this study is to evaluate the safety and immune response of an inactivated vaccine to prevent hand, foot and mouth disease (HFMD) caused by Enterovirus 71 (EV71).

Hand, foot and mouth disease (HFMD) caused by Enterovirus 71 (EV71) can be severely debilitating for some children with a risk of paralysis and death. The most susceptible age group is the 1 to 5 year olds, and the disease is spread via the oral-fecal route. Currently, there is no antiviral therapy nor there is a vaccine available to prevent HFMD. In this study, an inactivated vaccine (INV21) based on the EV71 antigen will be evaluated in terms of safety and immune response that is generated after two doses of the vaccine are given to healthy adults. Safety assessments include the frequency and severity of systemic adverse events as well as local reactions. Immune response will be assessed by measurement of EV71 neutralizing antibody levels at specified time points throughout the study.

Inclusion Criteria:

• Male or female aged 21 to 45 years, inclusive, at time of screening
• In good health as determined by medical history and physical examination.
• Normal clinical safety laboratory examinations.
• Body mass index (BMI) in the range 19-28 kg/m2.
• Documented negative serology for HIV, Hepatitis C antibody, and Hepatitis B surface antigen.
• Females of child bearing potential must have a negative urine pregnancy test result during screening and a negative urine pregnancy test immediately prior to vaccination.
• Willing and able to give written informed consent to participate.
• Willing and able to communicate with the Investigator and understand the requirements of the study.
• Low levels of EV71 neutralizing antibody.

Exclusion Criteria:

• 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
• Clinically significant hematological (including bleeding disorders), renal, hepatic, pulmonary (including asthma), central nervous system (including epilepsy, seizures, convulsions, or chronic migraines), cardiovascular, or gastrointestinal disorders, according to Investigator's judgment.
• Ongoing rash or other dermatologic disease.
• Abnormal ECG as assessed by the Investigator.
• History of diabetes mellitus.
• Hypersensitivity to any vaccine.
• History of severe HFMD with CNS involvement.
• Receipt of any vaccine in the 4 weeks preceding the first trial vaccination.
• Planned receipt of any vaccine in the 4 weeks following each of the vaccinations in this study.
• History of thymic pathology, thymectomy, myasthenia or any immunodeficiency.
• History of recurring migraines or on prescription medication for treatment of recurring headaches or migraines.
• Positive urine test for drugs of abuse.
• Females who are pregnant or lactating