The study is an observer-blind, randomized, controlled prospective intervention study of Phase I. The primary objective is to evaluate the safety and immunogenicity of the SARS-CoV-2 protein subunit recombinant vaccine adjuvanted with Alum+CpG1018

This trial is observer blinded, comparative, randomized, phase I study. Approximately 175 subjects will be recruited (18 years and above).

The investigational product is 0.5 ml in two dose-regimen (for all subjects) with 28 days apart between doses, compare to an active control (inactivated SARS-CoV-2 vaccine). There will be 4 formula of investigational product used with different concentration of Receptor Binding Domain (RBD) antigen and adjuvant CpG 1018.

Inclusion Criteria:

1. Clinically healthy subjects aged 18 years and above.
2. Subjects have been informed properly regarding the study and signed the informed consent form.
3. Subjects will commit to comply with the instructions of the investigator and the schedule of the trial.

Exclusion Criteria:

1. Subjects concomitantly enrolled or scheduled to be enrolled in another trial.
2. History of vaccination with any investigational product against COVID-19 (based on anamnesis)
3. Subjects who have history of COVID-19 (based on anamnesis or other examinations).
4. Evolving mild, moderate or severe illness, especially infectious disease or fever (body temperature ≥37.5℃, measured with infrared thermometer/thermal gun).
5. The result of RT-PCR test for SARS-CoV-2 is positive.
6. Women who are lactating, pregnant or planning to become pregnant during the study period (judged by self-report of subjects and urine pregnancy test results).
7. Abnormality hematology and biochemical test results (for main study subset).
8. History of asthma, history of allergy to vaccines or vaccine ingredients, and severe adverse reactions to vaccines, such as urticaria, dyspnea, and angioneurotic edema.
9. History of uncontrolled coagulopathy or blood disorders contraindicating intramuscular injection.
10. Patients with serious chronic diseases (serious cardiovascular diseases, uncontrolled hypertension and diabetes, liver and kidney diseases, malignant tumors, etc) which according to the investigator might interfere with the assessment of the trial objectives.
11. Subjects who have any history of confirmed or suspected immunosuppressive or immunodeficient state, or received in the previous 4 weeks a treatment likely to alter the immune response (intravenous immunoglobulins, blood-derived products or long-term corticosteroid therapy (> 2 weeks)).
12. Subjects who have history of uncontrolled epilepsy or other progressive neurological disorders, such as Guillain-Barre Syndrome.
13. Subjects receive any vaccination (other than COVID-19 vaccine) within 1 month before and after IP immunization.
14. Subjects plan to move from the study area before the end of study period.

Observer blind: Investigational Product and Active Comparator are masking. Lot number is masking