A Study to Evaluate The Efficacy, Safety and Immunogenicity of Inactivated SARS-CoV-2 Vaccines (Vero Cell) in Healthy Population Aged 18 Years Old and Above

This is a multicenter, randomized, double-blind, placebo-controlled study to evaluate the protective efficacy, safety and immunogenicity of inactivated SARS-CoV-2 vaccines in healthy population 18 years old and above. The participants were randomized into three groups of investigational vaccine 1, investigational vaccine 2 and placebo in a 1:1:1 ratio.2 doses of the investigational vaccine or placebo are inoculated into the deltoid muscle of the either arm according to the vaccination schedule of D0 \& D21 (+7 days).According to the immune durability results in Phase I/II study, and cross-neutralization assay results, a third dose (booster dose) generates a better immune response and is estimated to offer better protection, therefore, a booster dose will be given after 3 months