This study is an open phase Ⅲ clinical trial. The main purpose of this study is to evaluate Immunogenicity and safety of a third dose at different times after two-dose of COVID-19 vaccine (Vero cell), Inactivated manufactured by Sinovac Research & Development Co., Ltd. in the elderly aged 60 years and above.A total of 400 subjects aged 60 years and above who had received two doses of COVID-19 vaccine(Vero Cell), inactivated manufactured by Sinovac Research & Development Co., Ltd. between 3 - 6 months ago (100 subjects for 3 months, 4 months, 5 months and 6 months,respectively) will be enrolled and receive a third dose of two-dose of COVID-19 vaccine (Vero cell), inactivated were enrolled.
This is an open phase Ⅲ clinical trial of COVID-19 vaccine (Vero cell), inactivated manufactured by Sinovac Research & Development Co., Ltd.The purpose of this study is to evaluate Immunogenicity and safety of a third dose at different times after two-dose of COVID-19 vaccine (Vero cell), Inactivated in the Elderly Aged 60 years and above.