safety and immunogenicity study of booster vaccination in different doses of covid-19 vaccine (vero cell),inactivated for prevention of covid-19

Conditions: COVID-19

Summary: this is a randomized, double-blinded, phase ⅳ clinical trial of covid-19 vaccine (vero cell), inactivated manufactured by sinovac life sciences co. , ltd. the purpose of this study is to evaluate the safety and immunogenicity of booster vaccination using high-dosage or medium-dosage of covid-19 vaccine (vero cell), inactivated in populations who have completed primary immunization 5-9 months

this study a randomized, double-blinded, phase ⅳ clinical trial of covid-19 vaccine (vero cell), inactivated.the purpose of this study is to evaluate the safety and immunogenicity of booster vaccination using high-dosage or medium-dosage of covid-19 vaccine (vero cell), inactivated in populations who have completed primary immunization 5-9 months.a total of 340 subjects who have completed primary immunization using two-dose coronavac® 5-9 months were be enrolled.all of subjects were be randomly divided into two groups in a 1:1 ratio to receive high-dosage or medium-dosage of covid-19 vaccine (vero cell), inactivated.

Eligibility criteria:
inclusion criteria: * healthy participants aged 18 years and above; * 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 received two doses of inactivated covid-19 vaccine (coronavac®) manufactured by sinovac research \& development co., ltd and that is currently 5-9 months after the second dose. exclusion criteria: * history of sars-cov-2 infection(laboratory confirmed); * have received three and more doses of inactivated covid-19 vaccine; * known allergy to vaccines or vaccine ingredients, and serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneurotic edema; * 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 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; * 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.