Sponsor decided to cancel this trial.

This is a phase Ⅱb, single-center, randomized, double-blind, placebo-controlled study, to evaluate the immunogenicity and safety of the recombinant COVID-19 vaccine (Sf9 cells) in the subjects from healthy adults and elderly adults aged 18 years and above (aged 18-59 and 60-85 years) with immunization procedures 0, 21, 42 days and doses 40μg.

This is a phase Ⅱb, single-center, randomized, double-blind, placebo-controlled study, to evaluate the immunogenicity and safety of the recombinant COVID-19 vaccine (Sf9 cells) in the subjects from healthy adults and elderly adults aged 18 years and above (aged 18-59 and 60-85 years) . The phase Ⅱb clinical trials designed two research group, including adults group (aged 18-59 years) and elderly adults group (aged 60-85 years). Each group including 2000 participants. Vaccination or placebo group will be randomly assigned to receive in a 3:1 ratio, 4000 in total.

Inclusion Criteria:

• Aged 18-85 years old
• Able to understand the content of informed consent and willing to sign the informed consent.
• Able and willing to complete all the secluded study process during the whole study follow-up period (about 14 months).
• Axillary temperature ≤37.0℃

Exclusion Criteria:

• Positive serum immunoglobulin M (IgM) and immunoglobulin G (IgG) to the SARS-CoV-2.
• SARS-CoV-2 nucleic acid testing positive.
• History of SARS-CoV-2 infection or vaccination
• A Known History of HIV infection
• Family history of seizure, epilepsy, brain or mental disease.
• Participant that has an allergic history to any ingredient of vaccines.
• Woman who is pregnant, breast-feeding or positive in pregnancy test on day of enrollment, or is planning to be pregnant during the next 14 months.
• Any acute fever disease or infections.
• Have a medical history of SARS.
• Have serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension and not well-controlled.
• Major chronic illness, such as asthma, diabetes, or thyroid disease, and not well-controlled.
• Malignant tumor, activity or have been treated tumor and no clear have cured, or during the study period is likely to relapse.
• Hereditary angioneurotic edema or acquired angioneurotic edema.
• Urticaria in last one year.
• Asplenia or functional asplenia.
• Platelet disorder or other bleeding disorder may cause injection contraindication.
• Faint at the sight of blood or needles.
• Prior administration of immunodepressant or corticosteroids, antianaphylactics treatment, cytotoxic treatment in last 6 months.
• Prior administration of blood products in last 4 months.
• Prior administration of other research medicines in last 1 month.
• Prior administration of attenuated vaccine in last 1 month.
• Prior administration of subunit vaccine or inactivated vaccine in last 14 days.
• Nearly 7 days, all sorts of acute onset of disease or chronic diseases, such as receiving anti-tuberculosis treatment, history of asthma.
• According to the investigator's judgment, due to various medical, psychological, social or other conditions, it is contrary to the trial protocol or affects the subjects to sign informed consent.

Exclusion criteria for subsequent doses:

• Appear systemic allergic reaction, severe allergic reactions.
• Appear difficult to tolerate more than grade 3 adverse reactions.
• New discovery or a new happened after the first vaccination does not conform to the first dose of the inclusion criteria or conform to the first dose of exclusion criteria, determine whether or not to continue to participate in the study by the investigators.
• Investigators think of other reasons.