The trial includes two parts, namely the efficacy study and immunogenicity bridging study. A total of 34020 participants will be enrolled, i.e. 32820 for efficacy cohort, and 1200 for domestic immunogenicity cohort in China.~Efficacy study: Participants will be randomly inoculated with two doses of investigational vaccine or placebo according to 1:1 ratio following Day 0-Day 14 immunization schedule and will be observed from the first dose of investigational vaccine to collect symptomatic and laboratory-confirmed COVID-19 cases for the evaluation of the efficacy of the investigational vaccine.~Immunogenicity bridging study: Before inoculating the first dose, 14 days, 6 months and 12 months after the whole-course immunization, blood samples will be taken for determination of neutralizing antibody and IgG antibody against SARS-CoV-2 (ELISA method); and before inoculating the first dose, 6 months and 12 months after the whole-course immunization, blood samples will be taken for detecting specific T cells with the ELISPOT assay with an aim to evaluate immunogenicity and immune persistence.~Safety observations for all participants will be conducted from the first dose to 28 days after the whole-course immunization, and follow-up of SAEs will also be conducted from the first dose to at least 12 months after the whole-course immunization to evaluate the safety of the investigational vaccine.
This is a randomized, double-blinded, placebo controlled phase III clinical trial to evaluate the efficacy, safety and immunogenicity of SARS-CoV-2 Vaccine, Inactivated (Vero Cell) in adults aged 18 years and above after 2-dose schedule.