This is a randomized, double-blinded, Phase IIb clinical trial of 150 participants aged 18 years and above, who have completed two doses of mRNA COVID-19 vaccine as the primary vaccination for at least six months after the second dose. After enrollment, participants will be randomly assigned into two study arms at a ratio of 1:1 to receive a booster of one dose of medium-dose (600 SU) or one dose of high-dose (1200 SU) COVID-19 Vaccine.
This is a randomized, double-blinded, Phase IIb clinical trial of COVID-19 vaccine (CoronaVac®) manufactured by Sinovac Research & Development Co., Ltd.The purpose of this study is to evaluate to evaluate the changes in immunogenicity before and after the booster vaccine using the high (1200 SU) or medium (600 SU) dose of COVID-19 Vaccine (Vero Cell), Inactivated.