This study is a double-blind, randomized phase Ⅳ clinical trial of the inactivated SARS-CoV-2 vaccine (CoronaVac）manufactured by Sinovac Research & Development Co., Ltd. The purpose of this study is to evaluate the lot-to-lot consistency, immunogenicity and safety of CoronaVac in healthy adults aged 26-45 years.

This study is a double-blind, randomized phase Ⅳ clinical trial in healthy adults aged 26-45 years to evaluate the lot-to-lot consistency, immunogenicity and safety of the commercial-scale CoronaVac in healthy adults aged 26-45 years .The experimental vaccine was manufactured by Sinovac Research & Development Co.,Ltd. A total of 1080 healthy subjects aged 26 to 45 years old will be enrolled.The subjects will be randomly divided into three groups in a ratio of 1:1:1 to received two doses of vaccine on day 0 and day 28.

Inclusion Criteria:

• Healthy adults aged 26-45;
• The subjects can understand and voluntarily sign the informed consent form ;
• Proven legal identity.

Exclusion Criteria:

• Travel history / residence history of communities with case reports within 14 days prior to the study;
• History of contact with a SARS-CoV-2 infection (positive in nucleic acid test) within 14 days prior to the study;
• Have contacted patients with fever or respiratory symptoms from communities with case reports within 14 days prior to the study;
• 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 prior to the study;
• History of SARS-CoV-2 infection or receiving COVID-19 vaccine;
• 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 (Systemic lupus erythematosus)or immunodeficiency / immunosuppression(HIV,history after organ transplantation)
• 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;
• 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;
• Onset of various acute or chronic diseases within 7 days prior to the study;
• Axillary temperature >37.0°C;
• Already pregnant (including a positive urine pregnancy test) or are breastfeeding, planning to get pregnant within 2 months;
• The subjects participated in other clinical trials during the follow-up period, or will be planned 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.