In this study, a selected dose of the studied vaccine (JECEVAX) derived from phase 2 will be compared the safety with a licensed vaccine (JEVAX-VABIOTECH Vietnam) in Vietnamese children, aged 9-24 months to assess the safety and immunogenicity. Two hundred and twenty children are enrolled and randomly assigned into 2 groups (110 children/group), each of which receive 2 doses of investigate vaccines or control vaccine subcutaneously, at 28-34 days interval. Safety data included immediate reaction at the injection site and systemic reaction within 30 min of administration, solicited and unsolicited adverse events occurs from the 1st dose to 28-34 days after first dose (up to date of 2nd dose) and from the second dose to 28-34 days after 2nd dose (up to date of 3rd visit). SAE (from start of first dose to 28-34 days after second dose - date of 3rd visit).