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.
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.