Abstract: Objective To explore the safety of an inactivated enterovirus 71 vaccine in healthy people aged 6 months to 49 years. Methods A single-central, randomized, double-blind, placebo-controlled phase I clinical trial was conducted. Adult, adolescent, pediatric, and infant participants in Guangxi zhuang autonomous region were recruited. According to age and dose, participants were randomly divided into the low-dose experimental vaccine group, the high-dose experimental vaccine group, and the placebo-controlled group. Adverse events within 28 days and serious adverse events within 6 months after each dose of vaccine were observed and statistically analyzed. Results 1. A total of 200 subjects were recruited in this study (80 cases in the low-dose group, 80 cases in the high-dose group, and 40 cases in the placebo group), with a completion rate of 98.50% (100.00% in the low-dose group, 96.25% in the high-dose group, and 100.00% in the placebo group). 2. A total of 90 participants (45.00%) experienced 206 adverse events (AEs), including 1 vaccination-related AE leading to withdrawal and 1 vaccination-unrelated serious AE. 3. Systemic solicited adverse reactions occurred in 25 participants (12.50%) with 38 events, primarily manifesting as fever. Local solicited adverse reactions were reported in 19 participants (9.50%) with 23 events, predominantly characterized by pain and tenderness. Unsolicited adverse reactions occurred in 23 participants (11.50%) with 44 events, mainly upper respiratory tract infections. 4. The severity of adverse reactions was predominantly Grade 1 and Grade 2, with incidence rates of 17.50% and 10.50%, respectively, primarily presenting as fever and injection site pain. Three participants (1.50%) experienced Grade 3 adverse reactions, including fever and upper respiratory tract infections. Conclusion The EV71 investigational vaccine demonstrated a favorable safety profile in healthy individuals aged 6 months to 49 years.

Key words: Inactivated EV71 vaccine, Safety, Phase I clinical trial