Booster Dose of sIPV Co-administered With MMR and HepA-I.

Inclusion Criteria: * (1) healthy toddlers aged 18 months (+4 months); * (2) completed three doses of sIPV primary immunization; * (3) completed one dose of MMR vaccination; * (4) able to provide proof of vaccination; * (5) able to provide legal proof of identity; * (6) The guardians of the participants were able to understand and agree to sign the informed consent. Exclusion Criteria: * (1) a history of vaccination with a polio-containing vaccine component in addition to three sIPV primary doses, according to the vaccination certificate; * (2) have received a second dose of MMR vaccine or a vaccine containing a vaccine for measles, mumps or rubella, or hepatitis A vaccine (inactivated or attenuated), according to the vaccination certificate; * (3) previous history of polio or measles or mumps or rubella or hepatitis A; * (4) known severe allergy to the vaccine or vaccine components, such as urticaria, dyspnea, angioedema; * (5) severe congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc.; * (6) with autoimmune diseases or immunodeficiency diseases (including but not limited to systemic lupus erythematosus, asplenia, functional asplenia, and HIV infection); * (7) abnormal coagulation function (such as coagulation factor deficiency, platelet abnormality), or obvious bleeding, hematoma, or ecchymosis after previous intramuscular injection or venipuncture; * (8) have/have had a serious neurological disease (e.g., encephalopathy, epilepsy, convulsions \[other than febrile convulsions\]) or psychosis, a family history of neurological disease or psychosis; * (9) receiving immunosuppressive or other immunomodulatory therapy, cytotoxic therapy within the past 6 months, or planning to receive such treatment during the trial; * (10) have received an immune globulin or other blood products within the past 6 months or plan to receive such treatment during the trial; * (11) receipt of other investigational vaccines within 30 days before vaccination with the investigational vaccines; * (12) receipt of live attenuated vaccine within 28 days before vaccination with the investigational vaccine; * (13) receipt of subunit or inactivated vaccine within 7 days before vaccination with the investigational vaccine; * (14) acute diseases or acute episodes of chronic diseases within the past 7 days; * (15) Axillary temperature \>37.0℃ if fever occurred before vaccination; * (16) which are unsuitable for participation in the clinical trial as judged by the investigators.