A Study to Evaluate the Immunogenicity and Safety of a Recombinant Protein COVID-19 Vaccine SCTV01E-1 in Population Aged Above 18 Years

The study is a randomized, double-blind Phase II study. It will evaluate the immunogenicity and safety of SCTV01E-1. Approximately 400 participants aged 18 years and older will be enrolled in this study. 160 participants who have not been vaccinated with any COVID-19 vaccine will be enrolled in Cohort 1 and randomly assigned to the Group SCTV01E-1 and Group SCTV01E in a ratio of 1:1. All participants will receive 3 doses of vaccinations: Vaccination 1 on D0, Vaccination 2 on D28 and Vaccination 3 on D150. Participants in Group SCTV01E-1 will receive 3 doses of SCTV01E-1, and participants in Group SCTV01E will receive 3 doses of SCTV01E. 240 participants who were fully vaccinated with 2 or 3 doses of inactivated COVID-19 vaccines at least three months ago will be enrolled in Cohort 2 and randomly assigned to Group SCTV01E-1 and Group SCTV01E in a ratio of 1:1. All participants will receive 2 doses of vaccinations: Vaccination 1 on D0 and Vaccination 2 on D120. Participants in Group SCTV01E-1 will receive 2 doses of SCTV01E-1, and participants in Group SCTV01E will receive 2 doses of SCTV01E.