This Phase III study is a global multicenter, randomized, double-blind,placebo controlled clinical trial to evaluate the efficacy, safety, and immunogenicity of therecombinant COVID-19 vaccine (Sf9 cells) in 40,000 participants aged 18 years and older who do not have a known history of SARS-CoV-2 infection but whose locations or circumstances put them at appreciable risk of acquiring COVID-19 or SARS-CoV-2 infection.

This Phase III study is a global multicenter, randomized, double-blind, placebo-controlled clinical trial to evaluate the efficacy, safety, and immunogenicity of the recombinant COVID-19 vaccine (Sf9 cells) in 40,000 participants aged 18 years and older who do not have a known history of SARS-CoV-2 infection but whose locations or circumstances put them at appreciable risk of acquiring COVID-19 or SARS-CoV-2 infection. All participants will receive three doses of either study vaccine or placebo on Day 0, Day 21, Day 42 in a ratio of 1:1.There will be two cohorts in the study: the efficacy-safety cohort and the efficacy-extended safety-immunogenicity cohort. The efficacy will be evaluated in all vaccinated participants,including population in the efficacy-safety cohort, the efficacy-extended safety immunogenicity cohort. All vaccinated participants will also be followed up to monitor incidence of SAEs, MAAEs and AESIs. The reactogenicity of the vaccine will be evaluated in the efficacy-extended safety-immunogenicity cohort. Approximately 3000 participants will be enrolled into the efficacy-extended safety-immunogenicity cohort. This cohort will undergo additional visits to collect immunogenicity data associated with receiving the recombinant COVID-19 vaccine (Sf9 cells) and to analyze the infection status.

Inclusion Criteria:

• Aged 18 years and older.
• Able and willing (in the investigator's opinion) to comply with all study requirements.
• Willing to allow the investigators to discuss the volunteer's medical history with their general practitioner/personal doctor and access all medical records which are relevant to study procedures.
• Healthy adults, or stable-healthy adults who may have a pre-existing medical condition that does not meet any exclusion criteria. A stable medical condition is defined as a disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months before enrollment.
• For females of childbearing potential only, willingness to practice continuous effective contraception (see glossary) for 90 days after completion of 3 doses vaccination, and have negative pregnancy tests before each dose vaccination. Note: Nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal (defined as amenorrhea for ≥ 12 consecutive months prior to Screening without an alternative medical cause). A follicle-stimulating hormone (FSH) level may be measured at the discretion of the investigator to confirm postmenopausal status.
• Males participating in this study who are involved in heterosexual sexual activity must agree to practice adequate contraception (see glossary) and refrain from donating sperm for 90 days after receiving the study vaccination.
• Agreement to refrain from blood donation during the study.
• Provide a written informed consent form (ICF)

Exclusion Criteria:

Exclusion criteria for the first dose

• Participation in any other COVID-19 prophylactic drug trials during the duration of the study.

Note: Participation in COVID-19 treatment trials is allowed in the event of hospitalization due to COVID-19. The study team should be informed as soon as possible.

• Positive HIV antibody testing results.
• Participation in SARS-CoV-2 serological surveys where participants are informed of their serostatus during the duration of the study.

Note: Disclosure of serostatus post enrolment may accidentally unblind participants to group allocation. Participation in this trial can only be allowed if volunteers are kept blinded to their serology results from local/national serological surveys

• Planned receipt of any licensed or investigational vaccine, other than the study intervention,within 14 days before and after study vaccination.
• Prior receipt of an investigational or licensed COVID-19 vaccine.
• Administration of immunoglobulins and/or any blood products within three months prior to the planned administration of the investigational products (IPs).
• Any confirmed or suspected immunosuppressive or immunodeficient state; positive HIV status;asplenia; recurrent severe infections and chronic use (more than 14 days) of immunosuppressant medication within the past 6 months. Topical steroids or short-term (course lasting ≤14 days) oral steroids are not exclusion criteria.
• History of allergic disease or reactions likely to be exacerbated by any component of Recombinant COVID-19 Vaccine (Sf9 cells).
• Any history of angioedema
• Pregnancy, lactation, or willingness/intention to become pregnant within 90 days after receiving study vaccine
• Current diagnosis or treatment of cancer (except basal cell carcinoma of the skin and cervical carcinoma in situ)
• History of serious psychiatric condition likely to affect participation in the study
• A bleeding disorder (e g factor deficiency coagulopathy or platelet disorder) or prior history of significant bleeding or bruising following IM injections or venipuncture
• Suspected or known current alcohol or drug dependency
• Severe and/or uncontrolled cardiovascular disease, respiratory disease, gastrointestinal disease,liver disease, renal disease, an endocrine disorder, and neurological illness (mild/moderate well-controlled comorbidities are allowed)
• History of laboratory-confirmed COVID-19
• Continuous use of anticoagulants, such as coumarins and related anticoagulants (i.e. warfarin) or novel oral anticoagulants (i.e. apixaban, rivaroxaban, dabigatran, and edoxaban)
• Any other significant disease, disorder, or finding which may significantly increase the risk to the volunteer because of participation in the study, affect the ability of the volunteer to participate in the study, or impair interpretation of the study data.

Exclusion criteria for the second/third dose In this trial, the second/third dose vaccination may be terminated in some cases. These include systemic allergic reactions, severe hypersensitivity reactions, or intolerable grade 3 or higher adverse reactions after the previous vaccination/placebo. If these reactions occur, the participants should not continue to receive the second/third vaccination.