Safety of Sabin Inactivated Poliovirus Vaccine Administered Standalone or Concomitantly with Other Childhood Vaccines: A Real-World Study in China

<b>Background/Objectives</b>: Sabin strain-based inactivated poliovirus vaccine (sIPV) is increasingly used in China's routine immunization program and is often administered concomitantly with other childhood vaccines. However, large-scale real-world evidence on the safety of concomitant sIPV vaccination remains limited. This study evaluated the safety of sIPV administered standalone or concomitantly with other routine vaccines using provincial surveillance data. <b>Methods</b>: A retrospective observational study was conducted using data from the China National Adverse Events Following Immunization Surveillance System and the Anhui Provincial Immunization Information Management System. All sIPV doses administered between 1 November 2023 and 31 July 2025 were included. AEFI reporting rates per 100,000 doses were calculated. Descriptive analyses were performed by demographic characteristics and dose number. Multivariable negative binomial regression models were used to assess the association between vaccination mode and AEFI incidence, with dose-stratified analyses when appropriate. <b>Results</b>: Among the 303,526 sIPV doses analyzed (135,550 standalone and 167,976 concomitant), 188 AEFI cases were reported, yielding an overall reporting rate of 61.94 per 100,000 doses. Most AEFI were mild, self-limited general reactions, mainly fever and local injection-site reactions. Only two serious AEFI were reported, both resolving without sequelae. After adjustment for confounders, no significant difference in overall AEFI incidence was observed between standalone and concomitant vaccination (aRR = 0.97, 95% CI: 0.64-1.47). AEFI reporting was associated with age and region, while no consistent dose-related trend was identified. <b>Conclusions</b>: sIPV showed a favorable safety profile when administered standalone or concomitantly with other routine vaccines in real-world settings. Concomitant vaccination did not increase AEFI risk, supporting the continued use of sIPV in routine immunization programs.