A Phase III Clinical Trial to Determine the Safety and Efficacy of ZF2001 for Prevention of COVID-19

Inclusion Criteria: * Population aged 18 years and above; * Subjects voluntarily participate in the study and sign the informed consent form; and are able to provide valid identification, and understand and comply with the requirements of the trial protocol; * Female subjects of childbearing age agree to use effective contraceptive measures from the beginning of the study to 2 months after full course of vaccination. Exclusion Criteria: * Suspected or confirmed as fever(axillary temperature ≥37.3°C / oral temperature ≥37.5°C) within 72 hours before the enrollment, or axillary temperature ≥37.3°C / oral temperature ≥37.5°C at the day of screening; * Diastolic blood pressure ≥ 100mmhg and / or systolic blood pressure ≥ 150mmhg; * Patients with previous history of a COVID-19; * Detection of SARS-COV-2 nucleic acid or antibody is positive; * Those who are suffering from the following diseases: 1. With thrombocytopenia, any coagulation dysfunction or receiving anti-coagulatory treatment 2. Congenital or acquired immune deficiency or autoimmune disease history; no spleen, or history of splenic surgery and trauma, or receiving immunomodulator treatment within 6 months, e.g., immunosuppressive dose of glucocorticoids (reference dose: equivalent to 20mg/ day of prednisone, over 1 week); Or monoclonal antibodies; Or thymosin; Or interferon etc.; However, topical application (such as ointment, eye drops, inhalers or nasal sprays) is permitted; 3. Symptoms related to acute respiratory tract infection (such as sneezing, nasal congestion, runny nose, cough, sore throat, loss of taste, chills, shortness of breath, etc.); 4. Cancer patients (except basal cell carcinoma). * With a history of serious allergy to any vaccine or any composition of Investigational product (including: aluminum preparations), such as allergic shock, allergic throat edema, allergic purpura, thrombocytopenic purpura, localized allergic necrosis reaction (Arthus reaction), dyspnea and angioneuroedema; * Inoculated with subunit vaccine and inactivated vaccine within 14 days before the first dosing of investigational vaccine, or inoculated with attenuated live vaccine within 30 days; * Previous receiving blood transfusion or blood relevant products (including immunoglobulin) within 3 months, or planning to receive such products from the starting of study to \<6 months after the whole-course inoculation; * Have participated in or are participating in other covid-19 related clinical trials; * Women in breastfeeding period or in pregnant period (including women at childbearing age with positive result of urine pregnancy test); * Considered by investigators as any disease or state possibly making the subject at unacceptable risk; not conforming to the requirements of study protocol; interference of assessment of reactions of vaccine.