An Immunity Persistence Study of Sabin Inactivated Poliovirus Vaccine(Vero Cell) After Four Doses

Study Overview
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Brief Summary
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This is an open and observational follow-up clinical trial based on the previous Phase III clinical trial of Sabin Inactivated Poliovirus Vaccine manufactured by Sinovac Biotech Co. , the purpose of this study is to evaluate the immunity persistence of sIPV in infants after 4 doses of vaccination.

Detailed Description
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This study is an open and observational follow-up clinical trial based on the previous Phase III clinical trial of Sabin Inactivated Poliovirus Vaccine.The purpose of this study is to evaluate the immunity persistence of sIPV in infants after 4 doses of vaccination.A total of at least 450 subjects who have received 4 doses of the experimental vaccine or control vaccine will be enrolled,about 3.0ml of venous blood will be collected from each enrolled subject at the age of 4 years (48 to 54 months) and 5 years (78 to 84 months) after the last vaccination, respectively,and the serum will be separated for neutralizing antibody detection.The antibody levels of the experimental vaccine group and the control vaccine group will be compared to evaluate the immunity persistence of sIPV.

Official Title
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An Open and Observational Phase Ⅳ Clinical Trial to Evaluate the Immunity Persistence of Sabin Inactivated Poliovirus Vaccine (Vero Cell) After Four Doses

Conditions
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Poliomyelitis

Intervention / Treatment
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* Biological: Investigational sIPV
* Biological: Control IPV


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Subjects who have received 4 doses of experimental vaccine or control vaccine in phase Ⅲ clinical trials Exclusion Criteria: History of vaccination of other vaccine with poliovirus antigenic components except that of phaseⅢ clinical trial.

Ages Eligible for Study
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Minimum Age: 48 Months
Maximum Age: 84 Months

Sexes Eligible for Study
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All

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental Group<br>Subjects who have received 4 doses of the experimental vaccine (including subjects at the age of 4 years (48 to 54 months) and 5 years (78 to 84 months) after the last vaccination ) will be collected venous blood about 3.0ml. | Biological: Investigational sIPV<br>* Three intramuscular injections of the investigational vaccine (0.5 ml) at 0 month ,1 month and 2 months respectively; Single intramuscular injection of the investigational vaccine (0.5 ml) at 18 months<br>|
| Control Group<br>Subjects who have received 4 doses of control vaccine (including subjects at the age of 4 years (48 to 54 months) and 5 years (78 to 84 months) after the last vaccination ) will be collected venous blood about 3.0ml. | Biological: Control IPV<br>* Three intramuscular injections of the control vaccine (0.5 ml) at 0 month ,1 month and 2 months respectively;Single intramuscular injection of the control vaccine (0.5ml) at 18 months<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| All of participants with seroconversion rates of the neutralizing antibody of each group at the observation point wich at the age of 4 years (48 to 54 months) will be assessed | About 3.0ml of venous blood will be collected from all of the subjects at the age of 4 years (48 to 54 months) and all of the participants with seroconversion rates of the neutralizing antibody at the observation point wich at the age of 4 years (48 to 54 months) will be compared to evaluate the immunity persistence of SIPV. | At the age of 4 years (48 to 54 months) after the vaccination of the experimental vaccine or control vaccine | 
| All of participants with seroconversion rates of the neutralizing antibody of each group at the observation point wich in 5 years (78 to 84 months) after the last vaccination will be assessed | About 3.0ml of venous blood will be collected from all of the subjects in 5 years (78 to 84 months) after the last vaccination and all of the participants with seroconversion rates of the neutralizing antibody at the observation point which in 5 years (78 to 84 months) after the last vaccination will be compared to evaluate the immunity persistence of SIPV. | In 5 years (78 to 84 months) after the last vaccination of the experimental vaccine or control vaccine | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| All of participants with geometric mean titer (GMT) of each group at the observation point wich at the age of 4 years (48 to 54 months) will be assessed | All of participants with geometric mean titer (GMT) in experimental group and control group at the observation point wich at the age of 4 years (48 to 54 months) will be compared to evaluate the immunity persistence of SIPV. | At the age of 4 years (48 to 54 months) | 
| All of participants with geometric mean titer (GMT) of each group at the observation point wich in 5 years (78 to 84 months) after the last vaccination will be assessed | All of participants with geometric mean titer (GMT) in experimental group and control group at the observation point wich in 5 years (78 to 84 months) after the last vaccination of the experimental vaccine or control vaccine will be compared to evaluate the immunity persistence of SIPV. | In 5 years (78 to 84 months) after the last vaccination of the experimental vaccine or control vaccine |