Sequential Vaccination of Poliomyelitis Vaccine (Vero Cells), Inactivated, Sabin Strains From Different Manufacturers

Inclusion Criteria: * (1) Healthy infants of ≤ 12 months of age; * (2) Can provide proof of legal identity; * (3) Have completed two doses of sIPV vaccination at Beijing Institute; * (4) Able to provide proof of sIPV vaccination; * (5) The participant's guardian can understand and agree to sign the informed consent form. Exclusion Criteria: * (1) Known severe allergy to vaccines or vaccine components, such as urticaria, dyspnea, angioneurotic edema; * (2) Received immunoglobulins or other blood products, or plan to receive such treatment during the study; * (3) Received ≥14 days of immunosuppressive or other immunomodulatory therapy or cytotoxic therapy, or plan to receive such therapy during the study; * (4) Received another investigational vaccine within 28 days before receiving the study vaccine; * (5) Received a live attenuated vaccine within 14 days before receiving the trial vaccine; * (6) Received a subunit or inactivated vaccine within 7 days before receiving the trial vaccine; * (7) Acute exacerbation of various acute illnesses or chronic diseases within the last 7 days; * (8) Those who had a fever with an axillary temperature \>37.0°C before receiving the study vaccine; * (9) Participants who, in the judgment of the investigator, have any other factors that make them unsuitable for participation in the study.