The study is a randomized, double-blinded, active-controlled (Approved vaccine) Phase II clinical study. The study consists of 2 stages, Stage 1 and 2. In Stage 1, participants would randomly receive 2 doses of SCTV01C, SCTV01E, Sinopharm COVID-19 vaccine or mRNA vaccine on Day 0 and Day 28. Stage 1 is aimed to evaluate the immunogenicity and safety of SCTV01C or SCTV01E, comparing the immunogenicity data against Beta (B.1.351), Delta (B.1.617.2), Omicron (B.1.1.529) and other variants after the 2nd dose of vaccination with Sinopharm inactivated COVID-19 vaccine or mRNA vaccine. Stage 2 will start on Day 180 and the participants will receive a 3rd dose of vaccination.
The objective of the study is to evaluate the immunogenicity and safety of SCTV01C or SCTV01E, comparing the immunogenicity data against Beta (B.1.351), Delta (B.1.617.2), Omicron (B.1.1.529) and other variants with Sinopharm inactivated COVID-19 vaccine or mRNA vaccine.