Safety and Immunogenicity Study of Inactivated Vaccine for Prophylaxis of SARS CoV-2 Infection (COVID-19)

This study is a randomized, double-blinded, single-center, placebo-controlled phase Ⅰ/Ⅱ clinical trial in adults aged 18\~59 years. The purpose of this study is to evaluate the immunogenicity and safety of the experimental SARS-CoV-2 inactivated vaccine. The experimental vaccine and placebo were both manufactured by Sinovac Research \& Development Co., Ltd. A total of 744 subjects will be enrolled, with 144 at phase Ⅰ, and 600 at phase Ⅱ. All of participants in phase Ⅰ will be assigned to receive two doses of experimental vaccine or placebo on the schedule of day 0,14 or day 0,28.300 participants in phase Ⅱ will be assigned to receive two doses of experimental vaccine or placebo on the schedule of day 0,14 or day 0,28 and one dose of booster immunization will be given 6 months after primary immunization of day 0,14 or day 0,28.The other 300 participants in phase Ⅱ will be assigned to receive three doses of experimental vaccine or placebo on the schedule of day 0,14,42 or 0,28,56 .