Phase I Clinical Trial of Recombinant SARS-CoV-2 Spike Protein Vaccine (CHO Cell) for the Prevention of COVID-19

Inclusion Criteria: * Healthy individuals aged 18-59 years as well as 60 years and above who can provide legal identification (males and females are both required). * Willing to participate in the study with informed consent prior to screening * Negative in SARS-CoV-2 IgG and IgM test at screening. * Women of childbearing potential must be using effective method of birth control for 14 days prior to the enrollment of the study vaccine/placebo and must agree to continue such precautions during the study until 30 days after the second dose of the study vaccine/placebo. * Male subjects must agree to employ acceptable contraception from the day of first dose of the study vaccine/placebo until 30 days after the second dose of the study vaccine/placebo. Exclusion Criteria: * Confirmed or asymptomatic COVID-19 cases or SARS-CoV-2 infection(had positive in SARS-CoV-2 nucleic acid test or serological test). * Had a history of traveling or residence in domestic area of high and moderate pandemic risk, overseas or epidemic areas, or had a history of contact with confirmed, asymptomatic or suspected COVID-19 cases within the past 14 days; * History of SARS; * Received SARS-CoV-2 vaccines for emergency use or approved SARS-CoV-2 vaccines; * Individuals involving a clinical study within 6 months prior to the screening visit; or planning to participate in another clinical study during study period. * Clinical laboratory abnormalities and with clinical significance judged by investigator * Individual's systolic blood pressure ≥ 150mmHg and/or diastolic blood pressure ≥ 100mmHg at screening visit * Axillary temperature \>=37.3℃ prior to vaccination * Individuals in other acute diseases, or in the acute phase of chronic diseases within 3 days prior to the signing of the informed consent form. * Received immunoglobulin and/or blood product 3 months prior to the first vaccination. * Presence of uncontrolled chronic pulmonary, cardiovascular, renal, hepatic, neurologic, hematologic or metabolic (including diabetes mellitus) disorders, which would include the potential subject in a high-risk category for SARS-CoV-2 infection and/or its complications as judged by the investigator.. * Individuals with a history of severe allergic reaction (throat swelling, difficult in breath, dyspnea, or shock). * Individuals who have a history of severe adverse reaction associated with a vaccine or severe allergic reaction \[e.g., anaphylaxis to any component of the study vaccines (S protein, Aluminum hydroxide, CpG adjuvant). * Any autoimmune or immunodeficiency disease/condition \[e.g. human immunodeficiency virus (HIV) infection, Systemic lupus erythematosus (SLE)\] * Received immunoglobulin, blood-derived products within 3 months prior to the first study vaccination. * Abnormal coagulation function (such as coagulation factor deficiency, coagulation disease, platelet abnormality) obvious bruises or coagulopathy. * Pregnant women or breastfeeding women. * According to the judgment of the investigator, subject has or had any other symptoms, medical history and other factors that are not suitable for participating in this clinical trial.