This study is a randomized, double-blinded, and placebo controlled phase Ⅱ clinical trial of the SARS-CoV-2 inactivated vaccine to evaluate the safety and immunogenicity of the experimental vaccine in healthy adults ⩾18 years.

Inclusion Criteria:

1. Healthy permanent residents aged 18 years and above;
2. Subjects agree to sign the informed consent forms voluntarily;
3. Subjects are able to comply with the requirements of the clinical trial protocol;
4. Armpit temperature <= 37.0 degrees C;
5. Female subjects of childbearing age were not pregnant at the time of enrollment, were not breastfeeding, and had no birth plan within the first 3 months after enrollment; effective contraceptive measures had been taken within 2 weeks before enrollment.

Exclusion Criteria:

1. Within 14 days before vaccination, subjects have been abroad and to villages/communities experienced COVID-19 epidemics, and in contact with COVID-19 cases or suspected cases. Subjects are under isolation observation, or living in the villages/communities with COVID-19 cases or suspected cases;
2. Confirmed cases, suspected cases or asymptomatic cases with COVID-19 (refer to Information System of China Disease Prevention and Control);
3. Subjects with history of SARS virus infection by self-reported;
4. Positive in throat swab through RT-PCR;
5. Positive in SARS-CoV-2 antibody test;
6. Subjects with history of severe allergic reactions (such as acute anaphylaxis, urticaria, skin eczema, dyspnea, angioneurotic edema or abdominal pain) or allergy to known composition of inactivated SARS-CoV-2 vaccine;
7. Subjects with history of convulsion, epilepsy, encephalopathy or mental illness or family history;
8. Subjects with congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.;
9. Subjects with known or suspected diseases include: severe respiratory diseases, severe cardiovascular diseases, severe liver and kidney diseases, uncontrollable hypertension (systolic pressure >=140 mmHg, diastolic pressure >= 90 mmHg; subjects aged >= 60 years with systolic pressure >=150 mmHg, diastolic pressure >=100 mmHg), diabetic complications, malignant tumors, various acute diseases or acute onset of chronic diseases;
10. Subjects diagnosed with congenital or acquired immune deficiency, HIV infection, lymphoma, leukemia or other autoimmune diseases;
11. Subjects with history of coagulation dysfunction (e.g. Coagulation factor deficiency, coagulation disease);
12. Subjects receiving anti-TB treatment;
13. Subjects receiving other research drugs within 6 months before vaccination;
14. Subjects receiving immunotherapy or inhibitor therapy within 3 months (consistently oral or infusion for more than 14 days);
15. Subjects receiving blood products within 3 months before administration;
16. Subjects vaccinated with live attenuated vaccine within 14 days before vaccination;
17. Subjects vaccinated with other vaccine within 7 days before vaccination;
18. The researchers shall judge the other conditions which might be not in compliance with the requirements of this clinical trial.