Safety and Immunogenicity Study of Inactivated Vaccine for Prevention of COVID-19

This study is a randomized, double-blinded, single-center, placebo-controlled phase 1\&2 clinical trial in children and adolescents aged 3-17 years. The experimental vaccine and placebo were both manufactured by Sinovac Research \& Development Co., Ltd. A total of 552 subjects will be enrolled, with 72 at phase 1, and 480 at phase 2. Subjects will be assigned to receive two doses of different dosage of experimental vaccine or placebo on the schedule of day 0,28. Subjects in Phase receive the second dose 10 months or 12 months after the second dose.