This study replaced the 2nd and 3rd dose of Salk-IPV (produced by Sanofi) with Sabin-IPV (produced by CNBG) and then reviewed the safety and immunogenicity of the vaccination, aiming to acquire scientific evidence for the feasibility of immunization involving different viral strains replacement.

It is required by China Food and Drug Administration (CFDA) that considering in the real situation IPV receivers may be immuned by different viral strains of this vaccine, a phase 4 clinical trial aiming to demonstrate the safety and immunogenicity of the immunization schedule should be carried out. To be specific, the subjects were divided into 2 groups.

Group 1 received Salk-IPV+Sabin-IPV+Sabin-IPV respectively at the age of 2,3,4 months old.

Group 2 received Salk-IPV+Salk-IPV+Salk-IPV respectively at the age of 2,3,4 months old.

Blood sample was collected before vaccination and 30 days after the third dose of vaccination. Neutralization antibody against type I, Type II and Type III poliomyelitis virus were detected to evaluate the seroprotection rates and antibody geometric mean concentrations. The safety of both immunization schedule will also been monitored.

Inclusion Criteria:

• subjects aged from 60 days to 89 days old at the date of recruitment;
• with informed consent signed by parent(s) or guardians;
• parent(s) or guardians are able to attend all planned clinical appointments and obey and follow all study instructions;
• subjects did not receive any vaccines within 14 days;
• axillary temperature ≤37.0℃

Exclusion Criteria:

• allergic to any ingredient of vaccine or with allergy history to any vaccine;
• acute febrile disease or infectious disease;
• serious chronic diseases;
• any other factor that makes the investigator determines the subject is unsuitable for this study;