A Study to Evaluate Safety and Immunogenicity of Sequential Vaccination of Sabin Inactivated Poliomyelitis Vaccine (Vero Cell) and Live Attenuated Poliomyelitis Vaccine in Healthy 2-month-old Infants

Inclusion Criteria: 1. Healthy permanent residents aged 2 months (over 60 days and less than 90 days); 2. Infant's legal guardians agree to sign the informed consent forms voluntarily; 3. Infant's legal guardians are able to comply with the requirements of the clinical trial protocol; 4. Armpit temperature ≤ 37.0 ℃ Exclusion Criteria: 1. Preterm birth (delivery before the 37th week of pregnancy). 2. Previous vaccination against polio. 3. Congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc. 4. History of polio. 5. History or family history of convulsions, seizures, encephalopathy, and neurological disorder. 6. History of a serious reaction to any prior vaccination or known hypersensitivity to any component of the investigational vaccine. 7. Individuals with immunodeficiency or receiving immunosuppression therapy. 8. Disturbance of coagulation diagnosed by doctor (e.g., coagulation factors deficiency, coagulation disease, platelet abnormality) or obvious bruising or coagulation disorder. 9. Known or suspected concomitant diseases include: respiratory disease, acute infection or active chronic disease, cardiovascular disease, liver and kidney disease, skin disease, mother with HIV infection. 10. Administration of blood or blood-related products or immunoglobulins (hepatitis B immunoglobulins is acceptable). 11. History of administration of live attenuated vaccines within 14 days. 12. History of administration of subunit or inactivated vaccines within 7 days. 13. Individuals with any acute diseases within 7 days, receiving antibiotics or antiviral therapy. 14. Fever within 3 days (Armpit temperature ≥38.0 ℃). 15. Use of any investigational product recently, or have any conditions that the investigator believes may affect the evaluation of the trial.