BibTex format
@article{Gray:2026:10.1371/journal.pmed.1004952,
author = {Gray, E and Cooper, L and Ramirez, Gonzalez A and Mach, O and Derqui, N and Grassly, N and Blake, I},
doi = {10.1371/journal.pmed.1004952},
journal = {PLoS Medicine},
title = {Estimating population immunity against serotype-two poliomyelitis from the inactivated polio vaccine in routine immunization across 112 countries: a modelling study},
url = {http://dx.doi.org/10.1371/journal.pmed.1004952},
volume = {23},
year = {2026}
}
RIS format (EndNote, RefMan)
TY - JOUR
AB - BackgroundTo mitigate the risk of outbreaks of serotype 2 poliomyelitis after withdrawal of this serotype from oral poliovirus vaccine (OPV) in 2016, inactivated poliovirus vaccine (IPV) was introduced into the routine immunization (RI) programmes of all countries using OPV. Since 2022, WHO has recommended a 2-dose schedule, with a first dose at 14 weeks of age followed by a second dose at least 4 months later (e.g., 14–39 week schedule), although an earlier schedule may be adopted, despite lower immunogenicity, if vaccine coverage is low at older ages.Methods and findingsWe combined published data on type-2 IPV seroconversion with age, national RI coverage estimates, dose introduction dates, and country-specific schedules using a cohort model of population immunity to estimate IPV-induced immunity from 2024–2031 for 112 countries using either one or two doses of IPV. We projected immunity for current, 6–14, and 14–39 week schedules to find the optimal schedule and estimate the impact of interventions such as schedule changes and catch-ups. Under current schedules, estimated median serotype 2 population immunity in 2025 among children under five years of age is at 61% (IQR: 52%, 72%), rising to 71% (IQR: 57%, 80%) in 2031. The later 14–39 week schedule was optimal in all countries, with potential for the median immunity to rise to 78% (IQR: 66%, 85%) by 2031 if adopted by all countries in 2026. Eight countries would still have <50% immunity, rising to 65%−72% if catch-up campaigns with 80% coverage were implemented in 2030. The work is limited by the fact that IPV provides only a partial picture of total immunity where there has been emergency type-2 OPV use. Furthermore, national estimates may mask subnational coverage differences and pockets of extremely low immunity.ConclusionsUnder these estimates, IPV schedules and coverage are suboptimal in many countries. Those with a single dose should introduce a second on the 14&ndash
AU - Gray,E
AU - Cooper,L
AU - Ramirez,Gonzalez A
AU - Mach,O
AU - Derqui,N
AU - Grassly,N
AU - Blake,I
DO - 10.1371/journal.pmed.1004952
PY - 2026///
SN - 1549-1277
TI - Estimating population immunity against serotype-two poliomyelitis from the inactivated polio vaccine in routine immunization across 112 countries: a modelling study
T2 - PLoS Medicine
UR - http://dx.doi.org/10.1371/journal.pmed.1004952
VL - 23
ER -