Limited subjects

This is a randomized, Open, control phase Ⅳ clinical trial of inactivated COVID-19 vaccine manufactured by Sinovac Research & Development Co., Ltd,Beijing institute of Biological Products Co.,Ltd and Wuhan Institute of Biological Products Co.,Ltd.The purpose of this study is to explore booster Immunization of SARS-CoV-2 Inactivated Vaccine from different manufactures in adults aged 18-45 years old Previously Vaccinated with inactivated COVID-19 vaccine

This study a randomized, Open, control phase Ⅳclinical trial of inactivated COVID-19 vaccine .The purpose of this study is to explore booster Immunization of SARS-CoV-2 inactivated vaccine from different manufactures in adults aged 18-45 years old previously vaccinated with inactivated COVID-19 vaccine.A total of 480 subjects who have completed vaccination of two doses of inactivated COVID-19 vaccine for 6 to 8 months will be enrolled.In this study ,96 subjects who completed primary immunization with inactivated COVID-19 vaccine manufactured by Sinovac Research & Development Co.,Ltd. will receive one dose of booster immunization with inactivated COVID-19 vaccine manufactured by Sinovac Research & Development Co.,Ltd.(experimental group 1).192 subjects who completed primary immunization with inactivated COVID-19 vaccine manufactured by Beijing institute of Biological Products Co.,Ltd. will be randomly divided into two groups (experimental group 2 and experimental group 3) in a 1:1 ratio and receive one dose of booster immunization with inactivated COVID-19 vaccine manufactured by Sinovac Research & Development Co.,Ltd. and Beijing institute of Biological Products Co., Ltd,respectively.192 subjects who completed primary immunization with inactivated COVID-19 vaccine manufactured by Wuhan Institute of Biological Products Co.,Ltd.will be randomly divided into two groups(experimental group 4 and experimental group 5) in a 1:1 ratio and receive one dose of booster immunization with inactivated COVID-19 vaccine manufactured by Sinovac Research & Development Co.,Ltd. and Wuhan Institute of Biological Products Co.,Ltd.

Inclusion Criteria:

• Adults aged 18-45;
• Proven legal identity;
• The subjects can understand and voluntarily sign the informed consent form and be willing to complete the study in accordance with the study plan;
• Have completed two doses of SARS-CoV-2 inactivated vaccine vaccination for 6 to 8 months(the interval between the two doses vaccine of primary immunization is 21~35 days, and the two doses vaccine of primary immunization should be manufactured by the same manufactures).

Exclusion Criteria:

• History of SARS-CoV-2 infection(laboratory confirmed);

• Have received inactivated SARS-CoV-2 vaccine from other manufacturers other than Sinovac Life Sciences Co., Ltd.,Beijing Institute of Biological Products Co.,Ltd.and Wuhan Institute of Biological Products Co.,Ltd.and received three and more doses of inactivated SARS-CoV-2 vaccine;

• Severe adverse reactions, such as urticaria, dyspnea, and angioneurotic edema , occurred during the primary immunization;

• Autoimmune disease such as systemic lupus erythematosus or immunodeficiency / immunosuppression such as AIDS, post-transplant;

• 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;

• 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 other investigational drugs in the past 30 days;

• Receipt of attenuated live vaccines in the past 14 days;

• Acute diseases or acute exacerbation of chronic diseases within 7 days prior to booster vaccination;

• Axillary temperature >37.0°C;

• Already pregnant or are breastfeeding, planning to get pregnant within

  1months (according to subjects' self-report and urine pregnancy test results);

• Participated in other clinical trials prior to enrollment and during the followup period, or planned to participate in other clinical trials during the clinical trial period;

• According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.