The Serological Comparison Following Booster Dosage in Children Posttrivalent Oral Poliovirus Vaccine to Bivalent Oral Polio Vaccine–Inactivated Poliovirus Vaccine Switch: A Cross-sectional Study in Indian Children

India adopted this strategy by transitioning from tOPV to bOPV on 25 th April 2016.IPV was introduced into the Expanded Program on Immunization (EPI) in select states in November 2015, with nationwide implementation targeted by mid-2016.Due to global IPV supply constraints, India adopted a phased rollout of a IntroductIonPoliomyelitis, a highly infectious viral disease, has historically posed a significant global health burden.However, the introduction of 2 efficacious vaccines-the inactivated polio vaccine (IPV) and the oral polio vaccine (OPV)-since the 1950s has markedly reduced its incidence.The Global Polio Eradication Initiative (GPEI), launched in 1988, has been instrumental in this progress, achieving a >99% reduction in global polio cases. 1 Eradication efforts target both wild polioviruses (WPVs) and vaccine-derived polioviruses (VDPVs), necessitating comprehensive immunization strategies.The trivalent OPV (tOPV), containing all 3 poliovirus serotypes, was pivotal in eliminating WPV type 2 (WPV2), last detected in 1999 and declared eradicated in 2015, and WPV type 3 (WPV3), last reported in 2012. 1,2 Currently, endemic WPV transmission persists only in Pakistan and Afghanistan, underscoring the feasibility of global eradication.To mitigate the risk of circulating VDPVs (cVDPVs), particularly type 2, the GPEI's Polio Eradication and Endgame Strategic Plan (PEESP) 2013-2018 recommended the phased withdrawal of OPV. 3 In 2016, a globally synchronized switch from tOPV to bivalent OPV (bOPV), excluding the type 2 component, was implemented.Concurrently, IPV was introduced into routine immunization (RI) schedules to maintain type 2 immunity, with modeling studies projecting an 80-90% reduction in VDPV incidence following IPV introduction.