Immunogenicity and Safety of a Third Dose of COVID-19 Vaccine(Vero Cell), Inactivated in the Elderly

Study Overview
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Brief Summary
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This is an open phase Ⅲ clinical trial of COVID-19 vaccine (Vero cell), inactivated manufactured by Sinovac Research & Development Co., Ltd.The purpose of this study is to evaluate Immunogenicity and safety of a third dose at different times after two-dose of COVID-19 vaccine (Vero cell), Inactivated in the Elderly Aged 60 years and above.

Detailed Description
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This study is an open phase Ⅲ clinical trial. The main purpose of this study is to evaluate Immunogenicity and safety of a third dose at different times after two-dose of COVID-19 vaccine (Vero cell), Inactivated manufactured by Sinovac Research & Development Co., Ltd. in the elderly aged 60 years and above.A total of 400 subjects aged 60 years and above who had received two doses of COVID-19 vaccine(Vero Cell), inactivated manufactured by Sinovac Research & Development Co., Ltd. between 3 - 6 months ago (100 subjects for 3 months, 4 months, 5 months and 6 months,respectively) will be enrolled and receive a third dose of two-dose of COVID-19 vaccine (Vero cell), inactivated were enrolled.

Official Title
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An Open Clinical Trial to Evaluate Immunogenicity and Safety of a Third Dose at Different Times After Two-dose of COVID-19 Vaccine (Vero Cell), Inactivated in the Elderly Aged 60 Years and Above

Conditions
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COVID-19

Intervention / Treatment
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* Biological: COVID-19 Vaccine (Vero cell), Inactivated


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subjects aged 60 years and above; Provide legal identification; Have completed two-dose of COVID-19 vaccine (Vero cell), inactivated manufactured by Sinovac Research& Development Co., Ltd. for 3 6 months（The interval between two doses was 21 35 days）； Be able to understand and voluntarily sign the informed consent form and be willing to complete the study according to the research plan. Exclusion Criteria: History of SARS-CoV-2 infection(laboratory confirmed); Those who have received COVID-19 vaccine from other manufacturers other than Sinovac Research& Development Co., Ltd., or who have received booster immunization with COVID-19 vaccine after two doses of COVID-19 vaccine (Vero cell),inactivated manufactured by Sinovac Research& Development Co., Ltd.; History of serious adverse reactions to the vaccine or vaccine components, such as urticaria dyspnea and angioneuroedema; 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; Immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids(excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months or plan to receive these treatments during the study period; Receipt of blood products within in the past 3 months or plan to receive these treatments during the study period; Receipt of other investigational drugs in the past 30 days; Receipt of attenuated live vaccines in the past 14 days,or 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; According to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.

Ages Eligible for Study
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Minimum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Non-Randomized
Intervention Model: Parallel Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Experimental group 1 (3-month interval)<br>100 subjects who have received two doses of COVID-19 vaccine (Vero cell), Inactivated will receive a 3rd dose of the vaccine (3-month interval）. | Biological: COVID-19 Vaccine (Vero cell), Inactivated<br>* The COVID-19 vaccine,inactivated was manufactured by Sinovac Research& Development Co., Ltd.600SU inactivated SARS-CoV-2 CZ strain virus in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: CoronaVac®;|
| Experimental: Experimental group 2 (4-month interval)<br>100 subjects who have received two doses of COVID-19 vaccine (Vero cell), Inactivated will receive a 3rd dose of the vaccine (4-month interval）. | Biological: COVID-19 Vaccine (Vero cell), Inactivated<br>* The COVID-19 vaccine,inactivated was manufactured by Sinovac Research& Development Co., Ltd.600SU inactivated SARS-CoV-2 CZ strain virus in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: CoronaVac®;|
| Experimental: Experimental group 3 (5-month interval)<br>100 subjects who have received two doses of COVID-19 vaccine (Vero cell), Inactivated will receive a 3rd dose of the vaccine (5-month interval）. | Biological: COVID-19 Vaccine (Vero cell), Inactivated<br>* The COVID-19 vaccine,inactivated was manufactured by Sinovac Research& Development Co., Ltd.600SU inactivated SARS-CoV-2 CZ strain virus in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: CoronaVac®;|
| Experimental: Experimental group 4 (6-month interval)<br>100 subjects who have received two doses of COVID-19 vaccine (Vero cell), Inactivated will receive a 3rd dose of the vaccine (6-month interval）. | Biological: COVID-19 Vaccine (Vero cell), Inactivated<br>* The COVID-19 vaccine,inactivated was manufactured by Sinovac Research& Development Co., Ltd.600SU inactivated SARS-CoV-2 CZ strain virus in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: CoronaVac®;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Immunogenicity index-GMT of neutralizing antibodies | GMT of neutralizing antibodies at 14 days after vaccination | At 14 days after vaccination | 
| Immunogenicity index- GMT of neutralizing antibodies | GMT of neutralizing antibodies at 28 days after vaccination | At 28 days after vaccination | 
| Safety index-Incidence of adverse reactions | Incidence of adverse reactions 0 28 days after vaccination | 0 28 days after vaccination | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Immunogenicity index-seropositive rate of neutralizing antibodies | Seropositive rate of neutralizing antibodies of neutralizing antibodies before vaccination and at different points after vaccination | Day 0 before vaccination and 14 days, 28 days and 180 days after vaccination | 
| Immunogenicity index-GMT of neutralizing antibodies | GMT of neutralizing antibodies before vaccination and at different points after vaccination. | Day 0 before vaccination and 180 days after vaccination | 
| Immunogenicity index-4-fold increase rate of neutralizing antibodies | 4-fold increase rate of neutralizing antibodies at different points after vaccination. | At 14 days and 28 days after vaccination. | 
| Safety index-Incidence of adverse reactions | Incidence of adverse reactions 0 7 days after vaccination. | 0 7 days after vaccination | 
| Safety index-Incidence of serious adverse events | Incidence of serious adverse events 6 months after vaccination. | 6 months after vaccination |