An Immunity Persistence Study of Enterovirus 71 Inactivated Vaccine (Vero Cell)

Study Overview
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Brief Summary
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This is an open，observational and follow-up clinical trial based on the clinical trial of EV71 vaccine extended age group.The purpose of this study is to evaluate the immunity persistence of EV71 vaccine developed by Sinovac Biotech Co., Ltd in subjects aged 6  71 months after full immunization of two doses of vaccine.

Detailed Description
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This study is an open,observational and follow-up clinical trial of EV71 vaccine based on the clinical trial of EV71 vaccine extended age group.The main purpose of this study is to evaluate the immunity persistence of EV71 vaccine developed by Sinovac Biotech Co., Ltd in subjects aged 6 71 months after full immunization of two doses of vaccine.In this study, a total of 474 subjects from the EV71 vaccine extended age clinical trial who received two doses of experimental or control vaccine and were enrolled in the PPS set，including 274 subjects aged 6 35 months (the maximum number of subjects aged 6-23 months is 146, and the maximum number of subjects aged 24-35 months is 128),100 subjects aged 36 71 months and were enrolled in experimental group(EV71 vaccine developed by Sinovac Biotech Co., Ltd) and 100 subjects aged 36 71 months and were enrolled in control group(EV71 vaccine developed by Institute of Medical Biology,Chinese Academy of Medical Sciences) will be enrolled .Blood samples will be collected from subjects aged 6-23 months at 36 months after full immunization and at the age of 72 months.Blood samples will be collected from subjects aged 24 to 35 months at 36 months after full immunization.Blood samples will be collected from subjects aged 36-71 months at 36 months after the full immunization.

Official Title
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An Open, Observational Study to Evaluate the Immunity Persistence of an Inactivated Enterovirus 71 Vaccine (Vero Cell) in Subjects Aged 6 to 71 Months

Conditions
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Hand, Foot and Mouth Disease

Intervention / Treatment
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* Biological: Experimental Vaccine
* Biological: Control Vaccine


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subjects in the EV71 vaccine extended age clinical trial who received two doses of experimental or control vaccine and were enrolled in the PPS set; Provide legal identification; Participants or guardians of the participants should be capable of understanding the written consent form and voluntarily participate in the clinical trial. Exclusion Criteria: Vaccination history of vaccines containing EV71 antigen components other than the EV71 vaccine expanded age group clinical trial; History of hand, foot and mouth disease caused EV71; 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: 6 Months
Maximum Age: 71 Months

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 aged 6 23 months<br>Up to 146 subjects aged 6 23 months and have received EV71 vaccine developed by Sinovac Biotech Co., Ltd will be collected blood samples at 36 months after full immunization and at the age of 72 months. | Biological: Experimental Vaccine<br>* The EV71 vaccine was manufactured by Sinovac Biotech Co., Ltd and inactivated EV71 virus antigen was no less than 3.0EU in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: Enterovirus Type 71 Vaccine（Vero Cell）, Inactivated;|
| Experimental: Experimental Group aged 24 35 months<br>Up to 128 subjects aged 24 35 months and have received EV71 vaccine developed by Sinovac Biotech Co., Ltd will be collected blood samples at 36 months after full immunization . | Biological: Experimental Vaccine<br>* The EV71 vaccine was manufactured by Sinovac Biotech Co., Ltd and inactivated EV71 virus antigen was no less than 3.0EU in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: Enterovirus Type 71 Vaccine（Vero Cell）, Inactivated;|
| Experimental: Experimental Group aged 36 71 months<br>100 subjects aged 36 71 months and have received EV71 vaccine developed by Sinovac Biotech Co., Ltd will be collected blood samples at 36 months after full immunization . | Biological: Experimental Vaccine<br>* The EV71 vaccine was manufactured by Sinovac Biotech Co., Ltd and inactivated EV71 virus antigen was no less than 3.0EU in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: Enterovirus Type 71 Vaccine（Vero Cell）, Inactivated;|
| Active Comparator: Control Group aged 36 71 months<br>100 subjects aged 36 71 months and have received EV71 vaccine developed by Institute of Medical Biology,Chinese Academy of Medical Sciences will be collected blood samples at 36 months after full immunization . | Biological: Control Vaccine<br>* The EV71 vaccine was manufactured by Institute of Medical Biology,Chinese Academy of Medical Sciences ,and inactivated EV71 virus antigen was no less than 3.0EU in 0.5 mL of aluminium hydroxide solution per injection.<br>* Other names: Enterovirus Type 71 Vaccine, Inactivated（Human Diploid Cell）;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The seroconversion rates (SCR) of EV71 neutralizing antibody of all enrolled subjects | The seroconversion rates (SCR) of EV71 neutralizing antibody of all subjects at 36 months after full immunization. | At 36 months after full immunization | 
| The seroconversion rates (SCR) of the EV71 neutralizing antibody of subjects aged 6-23 months | The seroconversion rates (SCR) of the EV71 neutralizing antibody of subjects aged 6-23 months at the age of 72months. | At the age of 72 months | 
| GMT of the EV71 neutralizing antibody of all enrolled subjects | GMT of the EV71 neutralizing antibody of all enrolled subjects at 36 months after full immunization. | At 36 months after full immunization | 
| GMT of the EV71 neutralizing antibody of subjects aged 6-23 months | GMT of the EV71 neutralizing antibody of subjects aged 6-23 months at the age of 72months. | At the age of 72 months |