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

To evaluate the immunogenicity and safety of sequential vaccination with Sinovac sIPV among infants who have received two doses of Biological Products Co., Ltd. sIPV.

In this study, two hundred infants ≤ 12 months of age vaccinated with two doses of sIPV produced by Beijing Institute of Biological Products Co., Ltd., will be enrolled with a balanced male-to-female ratio. After enrollment with informed consent from the guardians of the participants, they will be divided into two groups, i.e., the study group and the control group, according to the 1:1 ratio. They will be vaccinated with one dose of the sIPV produced by Sinovac or the sIPV produced by Beijing Institute, respectively. The 30-minute observation will be conducted after the vaccination. Immediate reactions will be observed and solicited adverse events within 0-7 days, while unsolicited adverse events within 0-30 days will be collected to evaluate vaccine safety. About 2.5-3.0 ml of venous blood will be collected from all participants before and 30 days after vaccination, and anti-poliovirus type 1, type 2, and type 3 neutralizing antibody tests will be performed to evaluate immunogenicity.