Safety and Immunogenicity Study of Inactivated Vaccine for Prevention of COVID-19

Inclusion Criteria: * Healthy children and adolescents aged 3-17 years; * The subject and/or guardian can understand and voluntarily sign the informed consent form (double sign required for 8-17 years old); * Proven legal identity. Exclusion Criteria: * Travel history / residence history of communities with case reports within 14 days; * History of contact with a SARS-CoV-2 infection (positive in nucleic acid test) within 14 days; * Have contacted patients with fever or respiratory symptoms from communities with case reports within 14 days; * Two or more cases of fever and / or respiratory symptoms in a small contact area of volunteers, such as home, office etc. within 14 days; * History of SARS-CoV-2 infection; * History of asthma, history of allergy to the vaccine or vaccine components, or serious adverse reactions to the vaccine, such as urticaria, dyspnea, and angioedema; * Congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.; * Autoimmune disease or immunodeficiency / immunosuppression; * Severe chronic diseases, severe cardiovascular diseases, hypertension and diabetes that cannot be controlled by drugs, liver or kidney diseases, malignant tumors, etc.; * Severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; * Thyroid disease or history of thyroidectomy, spleenlessness, functional spleenlessness, spleenlessness or splenectomy resulting from any condition; * Diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation; * Immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months; * Physical examination has clinically significant abnormal hematology and biochemistry laboratory test results that exceed the reference value range (only applicable to phase I clinical trials): 1. Blood routine test: white blood cell count, hemoglobin, platelet count; 2. Detection of blood biochemical indicators: alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin (TBIL), creatinine (CR), fasting blood glucose; 3. Urine routine index: urine protein (PRO); * History of alcohol or drug abuse; * Receipt of blood products within in the past 3 months; * Receipt of other investigational drugs in the past 30 days; * Receipt of attenuated live vaccines in the past 14 days; * Receipt of inactivated or subunit vaccines in the past 7 days; * Acute diseases or acute exacerbation of chronic diseases in the past 7 days; * Axillary temperature \>37.0°C; * Already pregnant (including a positive urine pregnancy test) or are breastfeeding, planning to get pregnant within 3 months; * According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.