The experimental vaccine and placebo were both manufactured by Sinovac Research & Development Co., Ltd.

A total of 13.000 subjects will be enrolled. Participants will be assigned to receive two doses of experimental vaccine or placebo on the schedule of day 0,14. It is planned that the study will be conducted with two separate cohorts.

The first cohort will be healthcare workers in the high-risk group (K-1) and the second cohort will be people at normal risk (K-2). After 2 doses of vaccination of 1300 volunteers are completed, safety data will be evaluated by the data safety monitoring board without breaking the blinding, and if there is no safety issue, the K2 cohort will continue to be vaccinated.1.300 volunteers, including 650 volunteers SARS-CoV-2 vaccine and placebo arms, will be included in the K-1 cohort. In the K-2 cohort (normal risk group for COVID-19), 7.650 volunteers were planned to be included in the SARS-CoV-2 vaccine group, and 3.500 volunteers in the placebo group.