Clinical Study of the Third Dose Immunization Schedule of COVID-19 Inactivated Vaccine, (Vero Cells) in Adults Aged 18 Years and Above (6 Months After Two Doses)

Study Overview
=================
Brief Summary
-----------------
To evaluate the immunogenicity and safety of the third dose SARS-CoV-2 Vaccine, Inactivated (Vero Cell) in adults aged 18 years and above, who inoculated the third dose after 6 months since finished two doses schedule of CoronaVac or BBIBP-CorV.

Official Title
-----------------
Clinical Study of the Third Dose Immunization Schedule of COVID-19 Inactivated Vaccine, (Vero Cells) in Adults Aged 18 Years and Above (6 Months After Two Doses)

Conditions
-----------------
SARS-CoV-2 Infection

Intervention / Treatment
-----------------
* Biological: SARS-CoV-2 Vaccine, Inactivated (Vero Cell)


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: Axillary temperature ≤37.0 ℃. aged 18 years and above, after 6 months since finished two doses schedule of CoronaVac or BBIBP-CorV, or one does CoronaVac and one does BBIBP-CorV. Proven legal identity, could come each visit. Participants should understand the contents of the informed consent form, the vaccine in this trial, voluntarily sign the informed consent form. Exclusion Criteria: Persons with a clear history of SARS-CoV-2 infection. Using blood products after basic immunization or receiving immunosuppressive therapy. Participants who have a positive pregnancy test, or are breastfeeding, or plan to become pregnant, or plan to donate sperm or eggs from the screening to 6 months after vaccination. Allergic to the active substance in the vaccine, any inactive substance or substance used in the preparation process (aluminum hydroxide, glycine); History of abnormal clinical manifestations and serious diseases to be excluded, including but not limited to nervous system, cardiovascular system, blood and lymphatic system, immune system, kidney, liver, gastrointestinal tract, respiratory system, metabolism, bones and other system diseases, and a history of malignant tumors. Diseases beyond drug control, such as high blood pressure, diabetes, asthma. Those who developed acute disease within 2 weeks, or had symptoms of fever or upper respiratory tract infection within 7 days. Immunization with any vaccine within 14 days. Any other situations judged by investigators as not suitable for participating in this study.

Ages Eligible for Study
-----------------
Minimum Age: 18 Years

Sexes Eligible for Study
-----------------
All

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

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


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: two doses CoronaVac group<br>the third does was given 6 months after two doses CoronaVac group | Biological: SARS-CoV-2 Vaccine, Inactivated (Vero Cell)<br>* the third dose immunization schedule of SARS-CoV-2 inactivated vaccine<br>|
| Experimental: two doses BBIBP-CorV<br>the third does was given 6 months after two doses BBIBP-CorV | Biological: SARS-CoV-2 Vaccine, Inactivated (Vero Cell)<br>* the third dose immunization schedule of SARS-CoV-2 inactivated vaccine<br>|
| Experimental: first does CoronaVac and second does BBIBP-CorV<br>the third does was given 6 months after first does CoronaVac and second does BBIBP-CorV | Biological: SARS-CoV-2 Vaccine, Inactivated (Vero Cell)<br>* the third dose immunization schedule of SARS-CoV-2 inactivated vaccine<br>|
| Experimental: first does BBIBP-CorV and second does CoronaVac<br>the third does was given 6 months after first does BBIBP-CorV and second does CoronaVac | Biological: SARS-CoV-2 Vaccine, Inactivated (Vero Cell)<br>* the third dose immunization schedule of SARS-CoV-2 inactivated vaccine<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Seroconversion rate of Neutralizing and IgG antibodies against SARS-CoV-2 | Seroconversion rate of neutralizing antibodies and IgG against SARS-CoV-2 in serum for the third dose immunization schedule | From 0 days to 6 month after the third dose | 
| SARS-CoV-2 specific memory B and T cell response | SARS-CoV-2 specific memory B and T cell response for the third dose immunization schedule | From 0 days to 6 month after the third dose | 
| Adverse reactions/events rate | Occurence of adverse reactions/events after vaccination | 7 days after vaccination | 
| Adverse reactions/events rate | Occurence of adverse reactions/events after vaccination | 28 days after vaccination |