In this open labeled phase 1 clinical trial with enterovirus 71 (EV71) vaccine (ClinicalTrials.gov number: NCT01267903) performed in Donghai County, Jiangsu Province, China, in January 2011. A total of 100 healthy participants, stratified by age (40 adults aged 16-22 y and 60 children aged 6-15 y), were enrolled from volunteers and sequentially received EV71 vaccines of 160U (only for children), 320U, or 640U on day 0 and 28, in a manner of dose escalation. All the participants were followed for 28 d after each shot. During the study period, 37 participants reported at least one injection-site or systemic adverse reaction. No case of grade 3 adverse reaction or serious adverse event (SAE) was observed. Also no dose-related increase in reaction rate was noticed. Pain at injection-site and fever were the most frequently reported local and systematic reaction, respectively. The studied EV71 vaccines demonstrated acceptable tolerability and no anti-nuclear antibody (ANA) seropositive was detected pre or post vaccinations in participants. Also, no clinically significant abnormal change for the liver or kidney function indexes was found. In the according-to-protocol cohort for immunogenicity, it was observed one dose of EV71 vaccine elicited good immune response in the participants, especially for the ones with sero-positive baseline. No obvious dose-response relationship for immunogenicity was found.