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Circulating vaccine-derived polioviruses (cVDPVs) can emerge and lead to outbreaks of paralytic polio as well as asymptomatic transmission in communities with a high percentage of under-vaccinated children. Data from the WHO Polio Information System (POLIS) and the Global Polio Laboratory Network (GPLN) are used below to describe global polio outbreaks due to cVDPVs during January 2023-June 2024. This updates previous reports. During the reporting period, 74 cVDPV outbreaks were detected in 39 countries, predominantly in Africa. Of the outbreaks, 47 (64%) were new and were detected in 30 (77%) of the 39 countries. Three countries reported cVDPV type 1 (cVDPV1) outbreaks; 39 reported cVDPV type 2 (cVDPV2) outbreaks; and 2 countries reported co-circulating cVDPV1 and cVDPV2. Seventy cVDPV2 outbreaks were reported in 38 countries. cVDPV transmission lasted for >1 year into 2024 in 15 countries. In Nigeria and Somalia, countries with security-compromised areas, persistent cVDPV2 transmission has spread to neighbouring countries. Delayed implementation of outbreak response and low-quality campaigns have resulted in further international spread. Countries can control cVDPV outbreaks with timely allocation of resources to implement prompt, high-quality responses after outbreak confirmation. Stopping cVDPV transmission requires vaccination to increase population immunity; this requires overcoming barriers to vaccinating children. Des emergences de poliovirus circulants derives d'une souche vaccinale (PVDVc) peuvent se produire et donner lieu a des flambees epidemiques de poliomyelite paralytique et a une transmission asymptomatique dans les communautes comptant une forte proportion d'enfants sous-vaccines. Le present rapport, qui est une mise a jour des rapports precedents, s'appuie sur les donnees du Systeme d'information de l'OMS sur la poliomyelite (POLIS) et du Reseau mondial de laboratoires pour la poliomyelite (RMLP) pour decrire les flambees epidemiques de poliomyelite dues aux PVDVc qui sont survenues dans le monde entre janvier 2023 et juin 2024. Au cours de la periode couverte par ce rapport, 74 flambees de PVDVc ont ete detectees dans 39 pays, principalement en Afrique. Parmi elles, on compte 47 (64%) flambees nouvelles, dans 30 (77%) des 39 pays. Trois pays ont signale des flambees dues aux PVDVc de type 1 (PVDVcl), 39 pays ont notifie des flambees de PVDVc de type 2 (PVDVc2) et 2 pays ont fait etat d'une cocirculation de PVDVcl et de PVDVc2. Les flambees de PVDVc2 signalees dans 39 pays etaient au nombre de 70. Dans 15 pays, la transmission des PVDVc a dure >1 an, se poursuivant en 2024. Au Nigeria et en Somalie, pays dont certaines zones sont en proie a des problemes de securite, la transmission persistante des PVDVc2 s'est etendue aux pays voisins. La mise en oeuvre tardive des activites de riposte et la faible qualite des campagnes ont conduit a une propagation internationale supplementaire. Les flambees epidemiques de PVDVc peuvent etre endiguees rapidement si les pays deploient en temps utile les ressources necessaires a la mise en oeuvre d'une riposte rapide et de qualite une fois que l'epidemie est confirmee. Pour interrompre la transmission des PVDVc, il est essentiel d'accroitre l'immunite de la population grace a la vaccination, ce qui suppose de surmonter les obstacles qui entravent la vaccination des enfants., Introduction Live, attenuated oral poliovirus vaccine (OPV) induces long-term protection against paralytic disease and limits virus shedding in vaccinated people who are infected. (1) Circulating vaccine-derived polioviruses (cVDPVs) (2) occur [...]

Since the Global Polio Eradication Initiative (GPEI) began in 1988, the number of cases due to wild poliovirus (WPV) has decreased by > 99.99%. Five of the 6 WHO regions [...]

As of 1 May 2016, the use of oral poliovirus vaccine (OPV) type 2 for routine and supplementary immunization activities (SIAs) ceased after a synchronized global switch from trivalent OPV [...]

In 2022, global poliovirus modeling suggested that coordinated cessation of bivalent oral poliovirus vaccine (bOPV, containing Sabin-strain types 1 and 3) in 2027 would likely increase the risks of outbreaks and expected paralytic cases caused by circulating vaccine-derived polioviruses (cVDPVs), particularly type 1. The analysis did not include the implementation of planned, preventive supplemental immunization activities (pSIAs) with bOPV to achieve and maintain higher population immunity for types 1 and 3 prior to bOPV cessation. We reviewed prior published OPV cessation modeling studies to support bOPV cessation planning. We applied an integrated global poliovirus transmission and OPV evolution model after updating assumptions to reflect the epidemiology, immunization, and polio eradication plans through the end of 2023. We explored the effects of bOPV cessation in 2027 with and without additional bOPV pSIAs prior to 2027. Increasing population immunity for types 1 and 3 with bOPV pSIAs (i.e., intensification) could substantially reduce the expected global risks of experiencing cVDPV outbreaks and the number of expected polio cases both before and after bOPV cessation. We identified the need for substantial increases in overall bOPV coverage prior to bOPV cessation to achieve a high probability of successful bOPV cessation. [ABSTRACT FROM AUTHOR]

Circulating vaccine-derived polioviruses (cVDPVs) can emerge in areas with low poliovirus immunity and cause outbreaks (1) of paralytic polio. (2-6) Of the 3 types of wild poliovirus, type 2 was [...]

Widespread use of live, attenuated (Sabin) oral poliovirus vaccine (OPV) has resulted in marked progress towards global poliomyelitis eradication. (1) In under-immunized populations, however, extensive person-to-person transmission of Sabin poliovirus [...]

Due to the very low, but nonzero, paralysis risks associated with the use of oral poliovirus vaccine (OPV), eradicating poliomyelitis requires ending all OPV use globally. The Global Polio Eradication Initiative (GPEI) coordinated cessation of Sabin type 2 OPV (OPV2 cessation) in 2016, except for emergency outbreak response. However, as of early 2023, plans for cessation of bivalent OPV (bOPV, containing types 1 and 3 OPV) remain undefined, and OPV2 use for outbreak response continues due to ongoing transmission of type 2 polioviruses and reported type 2 cases. Recent development and use of a genetically stabilized novel type 2 OPV (nOPV2) leads to additional potential vaccine options and increasing complexity in strategies for the polio endgame. Prior applications of integrated global risk, economic, and poliovirus transmission modeling consistent with GPEI strategic plans that preceded OPV2 cessation explored OPV cessation dynamics and the evaluation of options to support globally coordinated risk management efforts. The 2022–2026 GPEI strategic plan highlighted the need for early bOPV cessation planning. We review the published modeling and explore bOPV cessation immunization options as of 2022, assuming that the GPEI partners will not support restart of the use of any OPV type in routine immunization after a globally coordinated cessation of such use. We model the potential consequences of globally coordinating bOPV cessation in 2027, as anticipated in the 2022–2026 GPEI strategic plan. We do not find any options for bOPV cessation likely to succeed without a strategy of bOPV intensification to increase population immunity prior to cessation. [ABSTRACT FROM AUTHOR]

In May 2016, the Global Polio Eradication Initiative (GPEI) coordinated the cessation of all use of type 2 oral poliovirus vaccine (OPV2), except for emergency outbreak response. Since then, paralytic polio cases caused by type 2 vaccine‐derived polioviruses now exceed 3,000 cases reported by 39 countries. In 2022 (as of April 25, 2023), 20 countries reported detection of cases and nine other countries reported environmental surveillance detection, but no reported cases. Recent development of a genetically modified novel type 2 OPV (nOPV2) may help curb the generation of neurovirulent vaccine‐derived strains; its use since 2021 under Emergency Use Listing is limited to outbreak response activities. Prior modeling studies showed that the expected trajectory for global type 2 viruses does not appear headed toward eradication, even with the best possible properties of nOPV2 assuming current outbreak response performance. Continued persistence of type 2 poliovirus transmission exposes the world to the risks of potentially high‐consequence events such as the importation of virus into high‐transmission areas of India or Bangladesh. Building on prior polio endgame modeling and assuming current national and GPEI outbreak response performance, we show no probability of successfully eradicating type 2 polioviruses in the near term regardless of vaccine choice. We also demonstrate the possible worst‐case scenarios could result in rapid expansion of paralytic cases and preclude the goal of permanently ending all cases of poliomyelitis in the foreseeable future. Avoiding such catastrophic scenarios will depend on the development of strategies that raise population immunity to type 2 polioviruses. [ABSTRACT FROM AUTHOR]

Nearly 3 decades after the World Health Assembly launched the Global Polio Eradication Initiative in 1988, 4 of the 6 WHO regions have been certified polio-free. (1) Nigeria is one [...]

On 10 August 2016, 2 years after the most recent wild poliovirus (WPV) case had been detected in Nigeria in July 2014, (1) 2 WPV cases were reported in the [...]

In 1988, the World Health Assembly resolved to eradicate poliomyelitis worldwide. In 2016, only 2 countries, Afghanistan and Pakistan, have endemic wild poliovirus (WPV) transmission. Nigeria was removed from the [...]

Background World Health Organization African region is wild poliovirus-free; however, outbreaks of vaccine-derived poliovirus type 2 (VDPV2) continue to expand across the continent including in Chad. We conducted a serological survey of polio antibodies in polio high-risk areas of Chad to assess population immunity against poliovirus and estimate the risk of future outbreaks. Methods This was a community-based, cross-sectional survey carried out in September 2019. Children between 12 and 59 months were randomly selected using GIS enumeration of structures. Informed consent, demographic and anthropometric data, vaccination history, and blood spots were collected. Seropositivity against all 3 poliovirus serotypes was assessed using a microneutralization assay at Centers for Disease Control and Prevention, Atlanta, GA, USA. Results Analyzable data were obtained from 236 out of 285 (82.8%) enrolled children. Seroprevalence of polio antibodies for serotypes 1, 2, and 3 was 214/236 (90.7%); 145/236 (61.4%); and 196/236 (86.2%), respectively. For serotype 2, the seroprevalence significantly increased with age (P =.004); chronic malnutrition was a significant risk factor for being type 2-seronegative. Interpretation Poliovirus type 2 seroprevalence in young children was considered insufficient to protect against the spread of paralytic diseases caused by VDPV2. Indeed, VDPV2 outbreaks were reported from Chad in 2019 and 2020. High-quality immunization response to these outbreaks is needed to prevent further spread. [ABSTRACT FROM AUTHOR]