Inclusion Criteria:

1. Age at the time of the first dose of vaccine: aged 18 to 59 years (including
boundary values) in the adult group, >=60 years old in the older group, regardless
of gender;

2. Axillary body temperature is less than 37.3 ℃ on the day of enrollment;

3. Based on the medical history and relevant physical examination and laboratory
examination results, the investigator clinically determined that the patient was in
good health;

4. Subjects have independent judgment ability, can read, understand and complete
vaccination diary cards, and they participate voluntarily and sign an informed
consent form.

Exclusion Criteria:

1. The subject has a history of SARS-CoV-2 infection, or has a history of contact with
SARS-CoV-2 infected persons (nucleic acid test positive) or suspected infected
persons within 30 days before screening, or living abroad within 30 days before
screening history;

2. Anyone who is allergic to any vaccines, drugs, foods or known excipients
(Dlin-MC3-DMA, cholesterol, distearoylphosphatidylcholine, PEG2000-DMG);

3. Have a history of SARS virus infection;

4. Upon questioning, have a history of COVID-19 vaccination, or have received other
inactivated vaccines within 14 days before screening, and received live attenuated
vaccines within 28 days;

5. Patients have a medical history or family history of epilepsy, convulsions or
convulsions, neurological diseases and mental diseases;

6. There are contraindications for intramuscular injection, such as: thrombocytopenia
that has been diagnosed, any coagulation disorder or receiving anticoagulant
treatment, etc.;

7. The investigator judges that he is known or suspected of having more serious
diseases at the same time, including but not limited to: respiratory diseases
(tuberculosis, lung failure, etc.), liver and kidney diseases, cardiovascular
diseases (heart failure, severe hypertension, etc.), Malignant tumor, infection or
allergic skin disease, HIV infection (test report can be provided), or during the
active period of acute infection or chronic disease (within 3 days before
vaccination);

8. Congenital malformations, developmental disorders, or chronic diseases that the
investigator judges are not suitable for participating in this study (such as Downs
syndrome, sickle cell anemia or neurological disorders, Guillain-Barre syndrome,
etc.), excluding stable diabetes/hypertension );

9. Patients with known immunological impairment or low immunological function diagnosed
by the hospital before enrollment, or functional asplenia or splenectomy caused by
any situation;

10. There is evidence that they are smokers (smokers >=10 cigarettes/day), alcoholics
(alcohol consumption >=4 units/day), drug abusers, and those who do not agree to
quit smoking or drinking during the trial;

11. Positive SARS-CoV-2 nucleic acid test and/or positive antibody test before the first
dose of vaccine, and/or abnormal imaging examination (small patchy shadow and
interstitial change, obvious peripheral lung zone, ground-glass shadow, infiltrating
shadow, lung consolidation, etc.), and/or decreased lymphocyte count;

12. Female: those who have a positive blood pregnancy test, are pregnant, breastfeeding,
or have a pregnancy plan within one year; men: whose spouse has a pregnancy plan
within one year;

13. Patients have participated in other clinical trials (drugs, biological products or
devices) within 3 months before the first dose of vaccine, or plan to participate in
other clinical trials during the research period;

14. Patients received immune enhancement or immunosuppressive therapy within 6 months
before the first dose of vaccine (continuous oral or instillation for more than 14
days);

15. Patients donated blood >=400 ml within 28 days before screening, or received whole
blood, plasma and immunoglobulin therapy within 6 months before screening;

16. Currently receiving research drug treatment to prevent COVID-19;

17. Patients are taking antipyretic, analgesic and anti-allergic drugs within 3 days
before enrollment;

18. The investigator judges that the subjects cannot follow the research procedures,
comply with the agreement, or plan to permanently relocate from the area before the
end of the research, or plan to leave the local area for a long time during the
scheduled visit period;

19. The relevant staff involved in this study or their immediate family members (such as
spouses, parents, siblings or children).

20. According to the investigator's judgment, there are other situations that are not
suitable for participating in this clinical trial.