2-Year Efficacy, Immunogenicity, and Safety of Vigoo Enterovirus 71 Vaccine in Healthy Chinese Children: A Randomized Open-Label Study

Background. This study evaluated the 2-year efficacy, immunogenicity, and safety of the Vigoo enterovirus 71 (EV71) vaccine. Method. In an initial phase 3 study, we randomly assigned healthy infants and children aged 6-35 months (ratio, 1: 1) to receive 2 doses of either EV71 vaccine (5120 participants) or placebo (5125 participants) at days 0 and 28, and followed them for 12 months after vaccination. In this extended follow-up study, we continued to evaluate the efficacy, immunogenicity, and safety of the EV71 vaccine for up to 2 years. Results. Overall efficacy was 94.84% (95% confidence interval [CI], 83.53%-98.38%) during the 2-year follow-up period (P <.0001), and the vaccine efficacy during the second year was 100.00% (95% CI, 84.15%-100.00%) against EV71-associated hand-foot-and-mouth disease (HFMD; P <.0001). Geometric mean titers of neutralizing antibody in participants remained high during the 2-year follow-up period, and no vaccine-related serious adverse events were recorded. Conclusions. Two doses of Vigoo EV71 vaccine could provide sustained protection against EV71-associated HFMD in healthy Chinese children.