Tolerability, Safety, and Immunogenicity of Tetravalent Inactivated Enterovirus Vaccine (Vero Cell).

Summary

The trial aims to assess the tolerability, safety, and immunogenicity of the tetravalent inactivated enterovirus vaccine in adults and children aged 6 months to 12 years. The main questions it aims to answer are: * Phase Ⅰ: The safety of the investigational vaccine in the target population based on adverse events (AEs); * Phase Ⅱ: The immunogenicity of the investigational vaccine in the target population. In Phase I, researchers will compare the safety of the investigational vaccine at low, medium, and high doses with the control vaccine; in Phase II, they will compare the safety and immunogenicity (including immune persistence) of the investigational vaccine at medium and high doses with the control vaccine. Procedure: * In Phase I, will be vaccinated with the investigational vaccine (at low, medium, and high doses) or the control EV71 vaccine/placebo in a 3:1 ratio, following a vaccination schedule of 0 and 1 month. Within each age group, and under the premise of ensuring safety, a dose-escalation trial will be conducted in reverse order of age. * In Phase II, participants in each age group will be randomly assigned to the medium-dose, high-dose investigational vaccine groups, and the control group in a 1:1:1 ratio, receiving two doses of the investigational vaccine or the EV71 vaccine (for ages 6-71 months)/placebo (for ages 6-12 years), with a one-month interval between the two doses. * For all participants in both Phase I and Phase II, immediate reactions within 30 minutes after each dose will be observed. Diary cards/contact cards will be used to collect solicited local and systemic adverse events (AEs) for 0-7 days and unsolicited AEs for 0-30 days after vaccination. Additionally, serious adverse events (SAEs) will be monitored from the start of vaccination until 6 months post-completion of the vaccination schedule. Furthermore, for participants of reproductive age in Phase I, pregnancy events will be collected.

Timeline

Start

2025-01-15

Primary completion

2025-12-30

Completion

2026-02-10

Drugs

Indications