To Evaluate the Immunogenicity and Safety of Sequential Booster Immunization of Recombinant Novel Coronavirus Vaccine (CHO Cells) for SARS-CoV-2

The experimental vaccine dose used in this study is 25μg/0.5mL. All subjects recruited should have received two doses of novel Coronavirus inactivated vaccine on the market for 6-9 months, and all eligible subjects will receive one dose of recombinant Novel Coronavirus vaccine (CHO cells).