Polio Cases Research Articles

Wastewater Surveillance for Poliovirus in Selected Jurisdictions, United States, 2022-2023.

Wastewater testing can inform public health action as a component of polio outbreak response. During 2022-2023, a total of 7 US jurisdictions (5 states and 2 cities) participated in prospective or retrospective testing of wastewater for poliovirus after a paralytic polio case was identified in New York state. Two distinct vaccine-derived poliovirus type 2 viruses were detected in wastewater from New York state and New York City during 2022, representing 2 separate importation events. Of those viruses, 1 resulted in persistent community transmission in multiple New York counties and 1 paralytic case. No poliovirus was detected in the other participating jurisdictions (Connecticut, New Jersey, Michigan, and Illinois and Chicago, IL). The value of routine wastewater surveillance for poliovirus apart from an outbreak is unclear. However, these results highlight the ongoing risk for poliovirus importations into the United States and the need to identify undervaccinated communities and increase vaccination coverage to prevent paralytic polio.

Increasing Population Immunity Prior to Globally-Coordinated Cessation of Bivalent Oral Poliovirus Vaccine (bOPV).

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.

Poliovirus on the rise in Pakistan amidst unprecedented floods and COVID-19 pandemic: An urgent concern.

Poliomyelitis is always a great concern in Pakistan and is a public health emergency. COVID-19 and recent floods have increased the challenge. This article highlights the situation of polio in Pakistan and also recommends several steps to eradicate the disease as early as possible. Selected articles were selected from electronic databases such as PubMed, Google Scholar, and Scopus using keywords such asWild Poliovirus, Vaccine Derived Polio Infection, Acute Flaccid Paralysis, Vaccine, and Pakistan. Polio infection has two types, wild poliovirus and vaccine-derived polio infection. 2019 and 2020 were a challenging time as cases were increased at that time in Pakistan. Acute flaccid paralysis is the most common complication of this disease. The maximum cases of polio are being reported from Khyber Pakhtunkhwa. A special public health importance should be given in this province. Regular vaccination and strict surveillance are important. It is also important to spread awareness among the people. Early identification and timely diagnosis are very important. Early diagnosis, proper timely treatment, vaccination, awareness, and community-based research will help Pakistan to eradicate this disease as early as possible.

Modelling the Time-varying Transmission of Wild Poliovirus in Pakistan

Aims/Objectives: The efforts to eradicate the wild poliovirus since 1988 have successfully reduced its global prevalence by 99%. However, as of 2024, Pakistan and Afghanistan remain the only two endemic countries facing the virus transmission. This study employs a transmission dynamic model to understand the persistence of wild poliovirus type 1 (WPV1) in Pakistan. Study Design: An ordinary differential equations-based deterministic type of mathematical model was developed. Place and Duration of Study: Department of Epidemiology and Public Health and Institute of Microbiology, University of Agriculture Faisalabad, March 2023 to August 2023. Methodology: We included the number of reported polio cases and the proportion of missed children by supplementary immunization activities (SIAs) across the country from 2017-2022. The model considered both human-human and environment-human virus transmission through sewage contamination and these are represented by time-dependent transmission rate parameters. The parameter estimation was done by model fitting to the reported data of WPV1 cases. The model simulations then predicted the future polio infections in Pakistan. Results: Our analysis identified that the asymptomatic infectious population missed by the SIAs is the major contributor to disease persistence in the country. Moreover, the environment can contribute to virus transmission in areas with poor WASH infrastructure and under-immunized populations. The estimated basic reproduction number through the next-generation matrix method was 1.61 while the estimated effective reproduction number was 0.12. The model showed a better predictive ability than constant transmission rate models. The numerical simulations considering the reduction in the virus-shedding rate by the asymptomatic population resulted in an 85% reduction in future polio cases in Pakistan. Conclusion: The results suggest that endemic virus transmission will continue subject to the current higher vaccination coverage across the country. The model can be further utilized to guide eradication efforts for targeted allocation of preemptive measures.

Progress Toward Poliomyelitis Eradication - Worldwide, January 2022-December 2023.

In 1988, poliomyelitis (polio) was targeted for eradication. Global efforts have led to the eradication of two of the three wild poliovirus (WPV) serotypes (types 2 and 3), with only WPV type 1 (WPV1) remaining endemic, and only in Afghanistan and Pakistan. This report describes global polio immunization, surveillance activities, and poliovirus epidemiology during January 2022-December 2023, using data current as of April 10, 2024. In 2023, Afghanistan and Pakistan identified 12 total WPV1 polio cases, compared with 22 in 2022. WPV1 transmission was detected through systematic testing for poliovirus in sewage samples (environmental surveillance) in 13 provinces in Afghanistan and Pakistan, compared with seven provinces in 2022. The number of polio cases caused by circulating vaccine-derived polioviruses (cVDPVs; circulating vaccine virus strains that have reverted to neurovirulence) decreased from 881 in 2022 to 524 in 2023; cVDPV outbreaks (defined as either a cVDPV case with evidence of circulation or at least two positive environmental surveillance isolates) occurred in 32 countries in 2023, including eight that did not experience a cVDPV outbreak in 2022. Despite reductions in paralytic polio cases from 2022, cVDPV cases and WPV1 cases (in countries with endemic transmission) were more geographically widespread in 2023. Renewed efforts to vaccinate persistently missed children in countries and territories where WPV1 transmission is endemic, strengthen routine immunization programs in countries at high risk for poliovirus transmission, and provide more effective cVDPV outbreak responses are necessary to further progress toward global polio eradication.

Use of a fractional dose of inactivated polio vaccine (fIPV) to increase IPV coverage among children under 5 years of age in Somalia

BackgroundGlobal efforts reduced incidence of polio cases from 350,000 in 1988 to 22 cases in 2022 globally. There have been no wild poliovirus (WPV) cases seen in Somalia since August 2014. However, in 2017, there was a surge in the number of cases of circulating vaccine-derived poliovirus type 2 (cVDPV2), even with different intervention responses using monovalent oral polio vaccine type 2 (mOPV2). This study aimed to assess the use of fractional inactivated polio vaccine (fIPV), a smaller dose of the polio vaccine, equal to 1/5 of a standard dose, as an innovative polio vaccination delivery model, and identify the main opportunities for and challenges to the use of fIPV in the future for vaccinations.MethodsThe study used two designs: a quasi-experimental design used to pilot fIPV in five districts and a cross-sectional study using both quantitative and qualitative approaches to collect primary data. A simple random sampling method was used to select 2 out of the 5 pilot districts for household surveys to study 768 participants. Key informant interviews and focus-group discussions were used to collect data from key frontline health workers and health/immunization officials involved in the campaigns. Secondary data from the pilot campaigns were analysed, such as administrative pilot data, lot quality assurance sampling (LQAS) and post-campaign communication assessments.ResultsA total of 131,789 children aged 4–59 months were included for the pilot. Among these, 126,659 (96.1%) and 126,063 (95.6%) children were vaccinated in rounds 1 and 2, respectively. Out of the 768 households assessed, 99.9% had their children vaccinated. Nearly half of the few children who were not vaccinated were reported to be due to the parent of the child not being at home (48%). Ninety-seven percent of the qualitative study interviewees were satisfied with fIPV injection and recommended its use for routine immunization.ConclusionsThe study findings are promising in the use of fIPV in mass campaigns to realize better coverage and global polio eradication. fIPV will potentially be used by policymakers in the design of polio eradication campaigns that integrate the fIPV vaccine into routine or supplementary immunization.

Is it time to switch to a formulation other than the live attenuated poliovirus vaccine to prevent poliomyelitis?

The polioviruses (PVs) are mainly transmitted by direct contact with an infected person through the fecal-oral route and respiratory secretions (or more rarely via contaminated water or food) and have a primary tropism for the gut. After their replication in the gut, in rare cases (far less than 1% of the infected individuals), PVs can spread to the central nervous system leading to flaccid paralysis, which can result in respiratory paralysis and death. By the middle of the 20th century, every year the wild polioviruses (WPVs) are supposed to have killed or paralyzed over half a million people. The introduction of the oral poliovirus vaccines (OPVs) through mass vaccination campaigns (combined with better application of hygiene measures), was a success story which enabled the World Health Organization (WHO) to set the global eradication of poliomyelitis as an objective. However this strategy of viral eradication has its limits as the majority of poliomyelitis cases today arise in individuals infected with circulating vaccine-derived polioviruses (cVDPVs) which regain pathogenicity following reversion or recombination. In recent years (between January 2018 and May 2023), the WHO recorded 8.8 times more cases of polio which were linked to the attenuated OPV vaccines (3,442 polio cases after reversion or recombination events) than cases linked to a WPV (390 cases). Recent knowledge of the evolution of RNA viruses and the exchange of genetic material among biological entities of the intestinal microbiota, call for a reassessment of the polio eradication vaccine strategies.

Geographic information system and information visualization capacity building: Successful polio eradication and current and future challenges in the COVID-19 era for the World Health Organization's African region.

Despite a half-century-long global eradication effort, polio continues to have a devastating impact on individuals and communities worldwide, especially in low-income countries affected by conflict or geographic barriers to immunization programs. In response, the World Health Organization (WHO) Global Polio Eradication Initiative (GPEI) employs disease surveillance and vaccination campaigns coordinated through the WHO Regional Office for Africa (AFRO) Geographic Information System (GIS) Centre. Established in 2017, the AFRO GIS Centre played a key role in the eradication of wild-type polioviruses (WPVs) in 2020, but the COVID-19 pandemic, emergence of circulating vaccine-derived polioviruses, and transmission of WPV1 from Central Asia have led to a resurgence of polio in Sub-Saharan Africa. The AFRO GIS comprises a set of mobile device or cloud-based tools for geospatial data collection, analysis, and visualization. Using tools such as Auto-Visual Acute Flaccid Paralysis Detection and Reporting, electronic surveillance, and Integrated Supportive Supervision, GIS personnel collect polio case numbers and locations, track field worker activities, follow the movements of nomadic populations vulnerable to polio and other diseases, and determine needs for further healthcare deployments. The system is location specific and operates in real time, enabling the AFRO GIS to promptly target its responses to polio, COVID-19, Ebola virus disease, and other public health crises and natural disasters. The present review describes the components of the AFRO GIS and how the AFRO GIS Centre coordinated on-the-ground polio eradication efforts to help secure Africa's certification as WPV free. It also examines current and prospective challenges regarding other disease outbreaks in the COVID-19 era and how the AFRO GIS Centre is addressing these ongoing public health needs.

Determinants of immunization in polio super high-risk union councils of Pakistan

BackgroundThe current polio epidemiology in Pakistan poses a unique challenge for global eradication as the country is affected by ongoing endemic poliovirus transmission. Across the country, 40 union councils (UCs) which serve as core reservoirs for poliovirus with continuous incidences of polio cases are categorized as super-high-risk union councils (SHRUCs). MethodologyA cross-sectional survey was conducted in 39 SHRUCs using a two-stage stratified cluster sampling technique. 6,976 children aged 12–23 months were covered. A structured questionnaire was used for data collection. Data were analyzed using STATA version 17. ResultsBased on both vaccination records and recall, 48.3% of children were fully-, 35.4 % were partially-, and 16.3% were non-vaccinated in the SHRUC districts. A child is considered fully vaccinated when h/she completed vaccination for BCG, OPV0, OPV 1-3, Penta 1-3, PCV 1-3, IPV, and MCV1. Vaccination cards were seen for over half of the children in the SHRUC districts of Khyber Pakhtunkhwa (KP) and the majority of the SHRUC districts in Sindh, except for the SHRUC district of Malir the districts of Balochistan.Results for polio vacancies show that 60.9% of children from the SHRUC districts were vaccinated with at least three doses of OPV and one dose of IPV, while 20.4% were vaccinated with any OPV doses or IPV and 18.7% of children did not receive any polio vaccines. The dropout rate between vaccine visits was higher than the WHO-recommended cutoff point of 10% for all vaccine doses in the SHRUC districts. The likelihood of being fully vaccinated was higher among the children of educated parents. Full vaccination was found significant among the children of any SHRUC districts compared to district Killa Abdullah. ConclusionContext-specific strategies with more focus on community engagement and targeted mobilization, along with robust monitoring mechanisms, would help address the underlying challenges of under-immunization in the SHRUCs.

Poliomyelitis alert on Tunisian borders: response and challenges

Abstract Introduction Poliomyelitis, which disappeared in Tunisia 30 years ago, should be the second disease to be eradicated after smallpox. However, a few endemic foci persist and its recent detection in some regions is causing great concern. On January 11, 2023, Tunisia received an alert with the notification of 2 polio cases in Algeria, the second of which was detected in November 2022 at about 400 KM from Tunisia. The objective of this study is to describe the results of the investigations following this alert as well as the prevention and response measures triggered. Methods We conducted an active search for acute flaccid paralysis (AFP) cases in all governorates and a retrospective search for possible unreported AFP cases hospitalized from November 1, 2022. Vaccination coverage was verified for catch-up if incomplete vaccination. Surveillance of poliovirus shedding in patients with primary immunodeficiencies (PIDs) was also conducted as well as other public health measures. Results As of April 20, 2023, 38 AFP cases have been reported through active search. Retrospective hospital-based surveillance has revealed 31 cases. In addition, 3142 children with deficient vaccination were identified, distributed differently by region. All of them were caught up with Inactivated polio vaccine (IPV). A total of 90 PIDs were followed up. The replacement of the Oral polio vaccine (OPV) dose at 6 months by IPV in the national immunization schedule as well as a request for verification of the possibility of using the new OPV2 in Tunisia and of the required requirements were made. Conclusions The risk of poliomyelitis resurgence in our country is not negligible. Sustained vigilance is necessary, particularly through ensuring high vaccination coverage and effective surveillance to rapidly detect any imported case. This is essential in view of the global context and the existence of outbreaks especially in certain African countries with which several exchanges and migratory flows remain. Key messages • The Poliomyelitis alert on Tunisian borders in January 2023 is a real threat, that should also be taken into consideration by neighboring countries. • Sustained vigilance is necessary, particularly through effective surveillance and appropriate vaccination strategy.

Modeling Poliovirus Transmission and Responses in New York State.

In July 2022, New York State (NYS) reported a case of paralytic polio in an unvaccinated young adult, and subsequent wastewater surveillance confirmed sustained local transmission of type 2 vaccine-derived poliovirus (VDPV2) in NYS with genetic linkage to the paralyzed patient. We adapted an established poliovirus transmission and oral poliovirus vaccine evolution model to characterize dynamics of poliovirus transmission in NYS, including consideration of the immunization activities performed as part of the declared state of emergency. Despite sustained transmission of imported VDPV2 in NYS involving potentially thousands of individuals (depending on seasonality, population structure, and mixing assumptions) in 2022, the expected number of additional paralytic cases in years 2023 and beyond is small (less than 0.5). However, continued transmission and/or reintroduction of poliovirus into NYS and other populations remains a possible risk in communities that do not achieve and maintain high immunization coverage. In countries such as the United States that use only inactivated poliovirus vaccine, even with high average immunization coverage, imported polioviruses may circulate and pose a small but nonzero risk of causing paralysis in nonimmune individuals.

Sensitive poliovirus detection using nested PCR and nanopore sequencing: a prospective validation study

Timely detection of outbreaks is needed for poliovirus eradication, but gold standard detection in the Democratic Republic of the Congo takes 30 days (median). Direct molecular detection and nanopore sequencing (DDNS) of poliovirus in stool samples is a promising fast method. Here we report prospective testing of stool samples from suspected polio cases, and their contacts, in the Democratic Republic of the Congo between 10 August 2021 and 4 February 2022. DDNS detected polioviruses in 62/2,339 (2.7%) of samples, while gold standard combination of cell culture, quantitative PCR and Sanger sequencing detected polioviruses in 51/2,339 (2.2%) of the same samples. DDNS provided case confirmation in 7 days (median) in routine surveillance conditions. DDNS enabled confirmation of three serotype 2 circulating vaccine-derived poliovirus outbreaks 23 days (mean) earlier (range 6–30 days) than the gold standard method. The mean sequence similarity between sequences obtained by the two methods was 99.98%. Our data confirm the feasibility of implementing DDNS in a national poliovirus laboratory.

The ghost of polio haunts us once again. The appeal of the scientific community is clear: “Vaccinate your kids today!”

IntroductionIn the summer of 2022, a vaccination campaign for the prevention of poliomyelitis was launched and “The CDC recommend that all children be vaccinated against polio, or poliomyelitis”. The scientific community is on the alert for new cases of polio, which is spreading. Although polio seemed to have been almost completely eradicated throughout the world, the disease has surprisingly reappeared in some Western countries. The risk of international spread of poliovirus remains a Public Health Emergency of International Concern (PHEIC). MethodThe authors reviewed recent polio cases in some western countries which have caused significant public health concern and they underline the meaning and weight of this issue emphasizing the importance of vaccination. DiscussionIn June 2022, the British authorities announced that they had detected traces of a form of polio derived from a vaccine strain in the wastewater of some London boroughs. Although no cases of disease were identified, the British government immediately announced that it was proceeding to reinstate polio vaccination for all children. A few weeks later, on July 18, 2022, the New Jersey Department of Health notified the CDCP of the detection of type-2 poliovirus in an unvaccinated young man in the New York metropolitan area. This case immediately triggered an appeal from the CDCP to get vaccinated and, above all, to vaccinate children.Low vaccination coverage means that the population is constantly at risk of further cases of paralytic poliomyelitis. ConclusionThe appeal to vaccinate children against polio is crucial, as prevention through vaccination is the only defense against the disease. We think that an efficient vaccination campaign can positively influence the process of eliminating the virus. At the same time, however, it demonstrates that simply lowering one's guard can quickly lead to a resurgence of polio cases. Hence, until polio is eradicated, we can be sure that contagion by the wild virus and the risk of vaccine-derived poliovirus will remain possible.

The Elephant’s Tail of VAPP, VDPV in the Polio End Game

A lot have been achieved by the Global Polio Eradication Initiative since 1988 after World Health Assembly passed the resolution to eradicate polio. Today, we have decreased the global polio incidence by 99.9% since GPEIs started working. We still have to remove polio from the few leftover pockets and get rid of the final 0.1% of polio cases. We have gained in positive terms that an estimated 16 million people today are walking and more than 1.5 million are alive because of the stakeholders’ strong, strategic and cooperative action. The journey to the last mile has some different difficulties and this article tries to provide additional insights into the strategies to achieve our goal of Polio eradication.

Worst-case scenarios: Modeling uncontrolled type 2 polio transmission.

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.

Polio-philanthropy in Africa: A narrative review.

Polio eradication efforts including polio-philanthropy have been coordinated and sustained since 1988, with the introduction of the Global Polio Eradication Initiative (GPEI). The polio fight is sustained in the name of evidence-based benevolence or beneficent philanthropy from which Africa has benefited immensely. With the recorded polio cases as of 2023, more efforts and funds are required to eradicate polio. Hence, it is not yet "Uhuru." Using the Mertonian lens, this study examines polio-philanthropy in Africa, its unintended consequences, and crucial dilemmas, which could impact the polio fight and polio-philanthropy. This is a narrative review that relies on secondary sources obtained through a thorough literature search. Only studies published in English were utilized. The study synthesized relevant literature in line with the study objective. The following databases were consulted: PubMed, philosopher's index, web of knowledge, Google Scholar, and Sociological Abstracts. Both empirical and theoretical studies were utilized for the study. Despite significant achievements, the global initiative has shortcomings when examined through the Mertonian lens of manifest and latent functions. The GPEI sets a unilinear goal within multiple challenges. The activities of the philanthropic giants manifest in disempowering rigor, multisectoral neglect, and parallel (health) systems, sometimes, inimical to the national health system. Most philanthropic giants often operate vertically. It is observed that, apart from funding, the last phase of polio-philanthropy will be defined by some crucial factors, the 4Cs: Communicable disease outbreaks, Conflict, Climate-related disasters, and Conspiracy theory, which could impact the prevalence or resurgence of polio. The polio fight will benefit from the persistent drive to reach the finish line as scheduled. The latent consequences or dysfunctions are general lessons for GPEI and other global health initiatives. Therefore, decision-makers should calculate the net balance of consequences within global health philanthropy for appropriate mitigation.

The Autumn Ghost. How the Battle Against a Polio Epidemic Revolutionized Modern Medical Care

The Autumn Ghost. How the Battle Against a Polio Epidemic Revolutionized Modern Medical Care

From Polio to COVID-19: Examining the Impact of Pandemics on Childhood Vaccination Programs.

This review article aims to examine the impact of pandemics on childhood vaccination programs, specifically looking at the examples of polio and coronavirus disease 2019 (COVID-19). The article provides a comprehensive overview of the history of polio vaccination programs, including the challenges of eradicating the disease and the barriers to vaccine uptake. The article also looks at the global efforts to eradicate polio, such as the Global Polio Eradication Initiative, and the progress made in reducing the number of polio cases worldwide. The article reviews the impact of the COVID-19 pandemic on childhood vaccination programs and how the pandemic has disrupted routine vaccination services. Lockdowns and travel restrictions have contributed to this, which has reduced access to medical facilities and vaccine uptake.The article also explores how the prioritization of COVID-19 vaccines has led to a diversion of resources away from routine childhood immunization programs. The article highlights the need to address these challenges to prevent a resurgence of vaccine-preventable diseases. Furthermore, the article discusses the lessons learned from these pandemics, such as the importance of global collaboration, vaccine equity, addressing vaccine hesitancy, pandemic preparedness, and embracing technology. The article emphasizes the need to prioritize vaccine equity andensure that vulnerable populations have access to vaccines. Additionally, the article stresses the importance of addressing vaccine hesitancy and providing effective communication and education about vaccines. The article also advocates for pandemic preparedness, emphasizing the need to invest in research and development of vaccines for emerging infectious diseases. Finally, the article suggests embracing technology as a means to improve vaccine accessibility and distribution.

The Fight against Poliovirus Is Not Over.

Poliovirus (PV), the virus that causes both acute poliomyelitis and post-polio syndrome, is classified within the Enterovirus C species, and there are three wild PV serotypes: WPV1, WPV2 and WPV3. The launch of the Global Polio Eradication Initiative (GPEI) in 1988 eradicated two of the three serotypes of WPV (WPV2 and WPV3). However, the endemic transmission of WPV1 persists in Afghanistan and Pakistan in 2022. There are cases of paralytic polio due to the loss of viral attenuation in the oral poliovirus vaccine (OPV), known as vaccine-derived poliovirus (VDPV). Between January 2021 and May 2023, a total of 2141 circulating VDPV (cVDPV) cases were reported in 36 countries worldwide. Because of this risk, inactivated poliovirus (IPV) is being used more widely, and attenuated PV2 has been removed from OPV formulations to obtain bivalent OPV (containing only types 1 and 3). In order to avoid the reversion of attenuated OPV strains, the new OPV, which is more stable due to genome-wide modifications, as well as sabin IPV and virus-like particle (VLP) vaccines, is being developed and offers promising solutions for eradicating WP1 and VDPV.

Prevalence of poliovirus neutralizing antibodies in Italian population: A systematic review and meta-analysis

IntroductionThe introduction of anti-poliomyelitis vaccines has driven progress toward the global eradication of wild polioviruses, a millennium goal of the World Health Organization. With the vaccination campaigns carried out since 1964, in 2002 Italy was certified polio-free, considering that no cases had been recorded since 1983. Nevertheless, it is crucial to guarantee high level of immunization coverage also in low-endemicity countries, considering that sporadic polio cases can be recorded. To evaluate the presence of susceptible subjects in the population, seroepidemiological studies are key actions. MethodsWe conducted a systematic review of the relevant literature to evaluate the prevalence of anti-PV neutralizing antibodies in Italian population. Seven studies, selected among scientific articles available in MEDLINE/PubMed, ISI Web of Knowledge and Scopus and published from January 1, 2012, to November 15, 2022, were included. ResultsThe pooled prevalence of subjects without PV1 neutralizing antibodies was 6.4% (95%CI = 0.5–16.9), for PV2 it was 5.3% (95%CI = 0.4–14.2), and for PV3 it was 13.0% (95%CI = 4.0–25.7; I2 = 98.5%). Levels of neutralizing antibodies appears to decrease with increasing age; this decline is a proxy for the real risk factor, which is the time since the last vaccine dose. ConclusionsPublic health institutions must be aware of the risk of reintroduction of wild PV in polio-free countries and therefore they must keep high level of immunization in population and reinforce the active surveillance systems.