{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,3]],"date-time":"2026-06-03T04:52:59Z","timestamp":1780462379714,"version":"3.54.1"},"reference-count":31,"publisher":"Public Library of Science (PLoS)","issue":"3","license":[{"start":{"date-parts":[[2026,3,19]],"date-time":"2026-03-19T00:00:00Z","timestamp":1773878400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100004423","name":"World Health Organization","doi-asserted-by":"publisher","award":["2024\/1500224-0"],"award-info":[{"award-number":["2024\/1500224-0"]}],"id":[{"id":"10.13039\/100004423","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100000265","name":"Medical Research Council","doi-asserted-by":"publisher","award":["MR\/X020258\/1"],"award-info":[{"award-number":["MR\/X020258\/1"]}],"id":[{"id":"10.13039\/501100000265","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosmedicine.org"],"crossmark-restriction":false},"short-container-title":["PLoS Med"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>To 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\u201339 week schedule), although an earlier schedule may be adopted, despite lower immunogenicity, if vaccine coverage is low at older ages.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods and findings<\/jats:title>\n                    <jats:p>We 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\u20132031 for 112 countries using either one or two doses of IPV. We projected immunity for current, 6\u201314, and 14\u201339 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\u201339 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 &lt;50% immunity, rising to 65%\u221272% 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.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Under these estimates, IPV schedules and coverage are suboptimal in many countries. Those with a single dose should introduce a second on the 14\u201339 week schedule; those on early schedules would benefit from adopting the 14\u201339 week schedule. IPV catch-up campaigns are recommended where RI coverage is low.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pmed.1004952","type":"journal-article","created":{"date-parts":[[2026,3,19]],"date-time":"2026-03-19T17:27:37Z","timestamp":1773941257000},"page":"e1004952","update-policy":"https:\/\/doi.org\/10.1371\/journal.pmed.corrections_policy","source":"Crossref","is-referenced-by-count":1,"title":["Estimating population immunity against serotype-two poliomyelitis from the inactivated polio vaccine in routine immunization across 112 countries: A modelling study"],"prefix":"10.1371","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6812-5334","authenticated-orcid":true,"given":"Elizabeth J.","family":"Gray","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Laura V.","family":"Cooper","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2963-6961","authenticated-orcid":true,"given":"Alejandro Ramirez","family":"Gonzalez","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ondrej","family":"Mach","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nieves","family":"Derqui","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nicholas C.","family":"Grassly","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3977-1318","authenticated-orcid":true,"given":"Isobel M.","family":"Blake","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2026,3,19]]},"reference":[{"issue":"5","key":"pmed.1004952.ref001","doi-asserted-by":"crossref","first-page":"791","DOI":"10.2217\/fmb.15.19","article-title":"Polio vaccination: past, present and future","volume":"10","author":"AS Bandyopadhyay","year":"2015","journal-title":"Future Microbiol"},{"issue":"9","key":"pmed.1004952.ref002","first-page":"73","article-title":"Poliomyelitis: intensification of the Global Eradication Initiative","volume":"89","author":"World Health Organization","year":"2014","journal-title":"Wkly Epidemiological Record"},{"issue":"35","key":"pmed.1004952.ref003","doi-asserted-by":"crossref","first-page":"934","DOI":"10.15585\/mmwr.mm6535a3","article-title":"Cessation of Trivalent Oral Poliovirus Vaccine and Introduction of Inactivated Poliovirus Vaccine - Worldwide, 2016","volume":"65","author":"LM Hampton","year":"2016","journal-title":"MMWR Morb Mortal Wkly Rep"},{"issue":"6489","key":"pmed.1004952.ref004","doi-asserted-by":"crossref","first-page":"401","DOI":"10.1126\/science.aba1238","article-title":"Evolving epidemiology of poliovirus serotype 2 following withdrawal of the serotype 2 oral poliovirus vaccine","volume":"368","author":"GR Macklin","year":"2020","journal-title":"Science"},{"issue":"12","key":"pmed.1004952.ref005","doi-asserted-by":"crossref","first-page":"1308","DOI":"10.3390\/vaccines12121308","article-title":"Monitoring the risk of type-2 circulating vaccine-derived poliovirus emergence during roll-out of type-2 novel oral polio vaccine","volume":"12","author":"CM Peak","year":"2024","journal-title":"Vaccines"},{"issue":"25","key":"pmed.1004952.ref006","first-page":"277","article-title":"Polio vaccines: WHO position paper \u2013 June 2022","volume":"97","author":"World Health Organization","year":"2022","journal-title":"Wkly Epidemiological Record"},{"key":"pmed.1004952.ref007","unstructured":"World Health Organisation. 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