Enterovirus 71 Infection

The purpose of this study is to evaluate the immunogenicity and safety of an inactivated Enterovirus Type 71 (EV71) vaccine, manufactured by Sinovac, in healthy Vietnamese children aged 6 to 71 months. Hand, Foot, and Mouth Disease (HFMD) is a common infectious disease in children, and EV71 is a major cause of severe complications and outbreaks in the Asia-Pacific region, including Vietnam. While this vaccine has demonstrated high efficacy and a favorable safety profile in previous clinical trials conducted in China, this study aims to generate specific bridging data for the Vietnamese pediatric population. This is a single-armed bridging clinical trial that plans to enroll approximately 320 healthy participants. Each participant will receive two doses of the EV71 vaccine administered intramuscularly on a 0 and 30-day schedule. The primary objective is to assess the seroconversion rate of neutralizing antibodies 30 days after the second dose. Safety will be assessed by monitoring the incidence of adverse reactions and serious adverse events (SAEs) throughout the study duration (approximately 2 months).