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

• 202-CoV low adjuvant dose (Biological): standard dose of 202-CoV with low dose CpG / alum adjuvant
• 202-CoV low antigen dose (Biological): low dose of 202-CoV with CpG / alum adjuvant
• 202-CoV standard dose (Biological): standard dose 202-CoV with CpG / alum adjuvant
• Placebo (Biological): Normal saline solution

Primary outcomes

• Geometric mean titer (GMT) of SARS-CoV-2 neutralising antibodies [56 days]: Neutralizing antibody activity as detected by neutralization assay expressed as GMTs at multiple time points through Day 56
• Seroconversion rate (SCR) of SARS-CoV-2 neutralising antibodies [56 days]: Neutralizing antibody activity as detected by neutralization assay expressed as seroconversion rate at multiple time points through Day 56
• Geometric mean titer (GMT) of serum IgG antibodies [56 days]: Serum IgG antibody levels specific for the SARS-CoV-2 S protein antigen as detected by ELISA expressed as GMTs at multiple time points through Day 56
• Seroconversion rate (SCR) of serum IgG antibodies [56 days]: Serum IgG antibody levels specific for the SARS-CoV-2 S protein antigen as detected by ELISA expressed as seroconversion rate at multiple time points through Day 56
• Geometric mean fold rise (GMFR) of SARS-CoV-2 neutralising antibodies [56 days]: GMFR in SARS-CoV-2 serum neutralizing titers from before vaccination to each subsequent time point
• Geometric mean fold rise (GMFR) of serum IgG antibodies [56 days]: GMFR of serum IgG antibodies from before vaccination to each subsequent time point

Secondary outcomes

• Percentage of participants reporting adverse events (AEs) [From dose 1 through 28 days after the last dose]: Percentage of participants with solicited AEs (local, systemic) for 28 days following each primary vaccination (Days 0, 28) by intensity, relevance.
• Percentage of participants reporting solicited AEs [For 7 days after dose 1 and dose 2]: Percentage of participants with solicited AEs (local, systemic) for 7 days following each primary vaccination (Days 0, 28) by intensity, relevance.
• Percentage of participants reporting unsolicited AEs [From dose 1 through 28 days after the last dose]: Percentage of participants with unsolicited AEs for 28 days following each vaccination
• Percentage of participants reporting serious adverse events (SAEs) [From dose 1 through 12 months after the last dose]: Percentage of participants with SAEs from dose 1 through 12month after last dose vaccination
• Percentage of participants reporting adverse events of special interest (AESIs) [From dose 1 through 12 months after the last dose]: Percentage of participants with AESI from dose 1 through 12month after last dose vaccination

Sex: All, ages: 18 Years to any, accepts healthy volunteers

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 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 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.
* 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.

• Results publication: Liu H, Zhou C, An J, Song Y, Yu P, Li J, Gu C, Hu D, Jiang Y, Zhang L, Huang C, Zhang C, Yang Y, Zhu Q, Wang D, Liu Y, Miao C, Cao X, Ding L, Zhu Y, Zhu H, Bao L, Zhou L, Yan H, Fan J, Xu J, Hu Z, Xie Y, Liu J, Liu G. Development of recombinant COVID-19 vaccine based on CHO-produced, prefusion spike trimer and alum/CpG adjuvants. Vaccine. 2021 Nov 26;39(48):7001-7011. doi: 10.1016/j.vaccine.2021.10.066. Epub 2021 Oct 30. PMID 34750014