Safety and Immunogenicity Study of an Inactivated SARS-CoV-2 Vaccine for Preventing Against COVID-19 in People Aged ⩾60 Years

This phase Ib/IIb trial is designed to evaluate the safety and immunogenicity of different doses of the Inactivated SARS-CoV-2 Vaccine based upon the randomized, double-blind and placebo-controlled principle. A total of 471 subjects aged ⩾60 years will be enrolled in the study, of which 96 and 375 will be enrolled for phase Ib and phase Ⅱb,respectively. The enrolled subjects in phase Ib receive two doses of low-, medium-, or high-dose of experimental vaccines or placebo at an interval of 28 days, while the enrolled subjects in Phase Ⅱb receive two doses of medium, high-dose experimental vaccines or placebo at an interval of 28 days.