Search

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 undervaccinated children. Using data from the World Health Organization Polio Information System and Global Polio Laboratory Network, this report describes global polio outbreaks due to cVDPVs during January 2023-June 2024 and updates previous reports. During the reporting period, 74 cVDPV outbreaks were detected in 39 countries or areas (countries), predominantly in Africa. Among these 74 cVDPV outbreaks, 47 (64%) were new outbreaks, detected in 30 (77%) of the 39 countries. Three countries reported cVDPV type 1 (cVDPV1) outbreaks and 38 countries reported cVDPV type 2 (cVDPV2) outbreaks; two of these countries reported cocirculating cVDPV1 and cVDPV2. In the 38 countries with cVDPV2 transmission, 70 distinct outbreaks were reported. In 15 countries, cVDPV transmission has lasted >1 year into 2024. In Nigeria and Somalia, both countries with security-compromised areas, persistent cVDPV2 transmission has spread to neighboring countries. Delayed implementation of outbreak response campaigns 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 all cVDPV transmission requires effectively increasing population immunity by overcoming barriers to reaching children., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

Since its launch in 1988, the Global Polio Eradication Initiative has made substantial progress toward the eradication of wild poliovirus (WPV), including eradicating two of the three serotypes, and reducing the countries with ongoing endemic transmission of WPV type 1 (WPV1) to just Afghanistan and Pakistan. Both countries are considered a single epidemiologic block. Despite the occurrence of only a single confirmed WPV1 case during the first half of 2023, Pakistan experienced widespread circulation of WPV1 over the subsequent 12 months, specifically in the historical reservoirs of the cities of Karachi, Peshawar, and Quetta. As of June 30, 2024, eight WPV1 cases had been reported in Pakistan in 2024, compared with six reported during all of 2023. These cases, along with more than 300 WPV1-positive environmental surveillance (sewage) samples reported during 2023-2024, indicate that Pakistan is not on track to interrupt WPV1 transmission. The country's complex sociopolitical and security environment continues to pose formidable challenges to poliovirus elimination. To interrupt WPV1 transmission, sustained political commitment to polio eradication, including increased accountability at all levels, would be vital for the polio program. Efforts to systematically track and vaccinate children who are continually missed during polio vaccination activities should be enhanced by better addressing operational issues and the underlying reasons for community resistance to vaccination and vaccine hesitancy., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

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., Competing Interests: All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. No potential conflicts of interest were disclosed.

Both inactivated poliovirus vaccine (IPV) and oral poliovirus vaccine (OPV) have contributed to the rapid disappearance of paralytic poliomyelitis from developed countries despite possessing different vaccine properties. Due to cost, ease of use, and other properties, the Expanded Programme on Immunization added OPV to the routine infant immunization schedule for low-income countries in 1974, but variable vaccine uptake and impaired immune responses due to poor sanitation limited the impact. Following launch of the Global Polio Eradication Initiative in 1988, poliomyelitis incidence has been reduced by >99% and types 2 and 3 wild polioviruses are now eradicated, but progress against type 1 polioviruses which are now confined to Afghanistan and Pakistan has slowed due to insecurity, poor access, and other problems. A strategic, globally coordinated replacement of trivalent OPV with bivalent 1, 3 OPV in 2016 reduced the incidence of vaccine-associated paralytic poliomyelitis (VAPP) but allowed the escape of type 2 vaccine-derived polioviruses (VDPV2) in areas with low immunization rates and use of monovalent OPV2 in response seeded new VDPV2 outbreaks and reestablishment of type 2 endemicity. A novel, more genetically stable type 2 OPV vaccine is undergoing clinical evaluation and may soon be deployed prevent or reduce VDPV2 emergences., (© The Author(s) 2021. Published by Oxford University Press for the Infectious Diseases Society of America.)

Introduction: inspite of the demonstrable evidence of the preventive and protective ability of vaccines to reduce the outbreak of vaccine-preventable diseases, there are still some significant disease outbreaks recorded in our communities. In some settings, these outbreaks have been linked with poor vaccine management. Therefore, this study was conducted to compare the cold chain practices in Oyo State, Nigeria., Methods: we conducted a cross-sectional survey among health workers in the local government areas of Oyo State between October and November 2019. Using purposive sampling, we recruited all the 84 routine immunization focal persons for the study. A self-administered questionnaire was used to collect data on cold chain management. Data were analyzed using SPSS version 24 and bivariate analysis was done using Chi-square. Statistical significance was set at p < 0.05., Results: the mean age of the respondents was 46.4 ± 6.7 years. Most prevalent cadre in the rural facilities was health assistants (87.5%) while Community Extension Health Workers (54.8%) were prevalent in the urban (p = 0.002). The proportion of respondents with adequate cold chain equipment was significantly higher in the urban compared with the rural area. The cold boxes were the only adequate cold chain equipment found in the rural health facilities compared with the urban (p = 0.036)., Conclusion: there was a low proportion of qualified health workers and inadequate cold chain equipment in the rural area compared with the urban facilities. Engagement of skilled health workers and supply of the cold chain equipment are recommended., Competing Interests: The authors declare no competing interests., (Copyright: Olaniyan Akintunde Babatunde et al.)

Objectives : Wild poliovirus (WPV) infection has been eliminated in Europe through mass immunization. Resettling refugees may lack immunity and importing WPV through refugees continues to cause concerns. Method : We performed a cross-sectional study to establish the prevalence of poliovirus immunity in children and adult refugees resettling in Aarhus, Denmark. Immunity was evaluated by antibody response for serotypes 1, 2, and 3. Results : The participants in this study counted a total of 475 children and adult refugees aged between 6 months and 76 years and 59% were males. The survey was conducted between 2014 and 2016. Among the refugees, 72% were from Syria, and the rest from Eritrea, Congo, Lebanon, Somalia, Afghanistan, Iran, Iraq, Ethiopia, and Columbia. In the cohort, 27 lacked antibodies against a least one serotype. None of the participants lacked antibodies against all three polio types. Originating from The Horn of Africa, age between 20 and 30 and male gender was associated with lack of immunity. Conclusion : The study found a complete WPV immunity in 94% of recently resettled refugees in Denmark. This study demonstrates a high coverage of the polio immunization program. However, ensuring poliovirus immunity among refugees remains a priority until polio has been eradicated worldwide.

Introduction: The prevalence of HIV infection in South African pregnant women has been approximately 30% over the past decade; however, there has been a steady decline in mother-to-child transmission of HIV from 8% in 2008 to <2% in 2015. We evaluated the immunogenicity of live-attenuated trivalent oral polio vaccine (OPV) following the primary vaccination series (doses at birth, 6, 10 and 14 weeks of age) in HIV-exposed uninfected (HEU), HIV-infected infants initiated on early anti-retroviral treatment (HIV+/ART+), HIV-infected infants on deferred ART (HIV+/ART-) and HIV-unexposed infants (HU) as the referent group., Methods: Serum polio neutralization antibody titres were evaluated to serotype-1, serotype-2 and serotype-3 at 6, 10 and 18 weeks of age. Antibody titres ≥8 were considered seropositive and sero-protective., Results: At 18 weeks of age, following the complete primary series of four OPV doses, no differences in GMTs, percentage of infants with sero-protective titres and median fold change in antibody titre (18 weeks vs 6 weeks) were observed in HEU infants (n = 114) and HIV+/ART+ infants (n = 162) compared to HU infants (n = 104) for the three polio serotypes. However, comparing HIV+/ART- infants (n = 70) to HU infants at 18 weeks of age, we observed significantly lower GMTs for serotype-1 (p = 0.022), serotype-2 (p<0.001) and serotype-3 (p<0.001), significantly lower percentages of infants with sero-protective titres for the three serotypes (p<0.001), and significantly lower median fold change in antibody titre for serotype-1 (p = 0.048), serotype-2 (p = 0.003) and serotype-3 (p = 0.008)., Conclusion: Delaying initiation of ART in HIV-infected infants was associated with an attenuated immune response to OPV following a four-dose primary series of vaccines, whereas immune responses to OPV in HIV-infected children initiated on ART early in infancy and HEU children were similar to HU infants., Competing Interests: The authors have declared that no competing interests exist.

Acute flaccid paralysis (AFP) surveillance is key for global polio eradication. It allows detecting poliovirus (PV) reintroductions from endemic countries. This study describes AFP surveillance in Spain from 1998 to 2015. During this time, 678 AFP cases were reported to the Spanish National Surveillance Network. The mean notification rate was 0.58 AFP cases/100,000 population under 15 years old (range: 0.45/100,000-0.78/100,000). Two periods (P) are described: P1 (1998-2006) with the AFP notification rate ranging from 0.66/100,000 to 0.78/100,000, peaking in 2001 (0.84/100,000); and P2 (2007-2015) when the AFP rate ranged from 0.43/100,000 to 0.57/100,000, with the lowest rate in 2009 (0.31/100,000). No poliomyelitis cases were caused by wild PV infections, although two Sabin-like PVs and one imported vaccine-derived PV-2 were detected. Overall, 23 (3.4%) cases met the hot case definition. Most cases were clinically diagnosed with Guillain-Barré syndrome (76.9%; 504/655). The adequate stool collection rate ranged from 33.3% (7/21) to 72.5% (29/40). The annual proportion of AFP cases with non-polio enterovirus findings varied widely across the study period. AFP surveillance with laboratory testing for non-polio enteroviruses must be maintained and enhanced both to monitor polio eradication and to establish sensitive surveillance for prompt detection of other enteroviruses causing serious symptoms.

Objectives: To assess the prevalence of protective antibody titers to polioviruses in adults candidates for solid organ transplant (SOT), and to assess the immunogenic response to inactivated polio vaccine in this population., Methods: The study included SOT candidates referred to Immunization Reference Centre of Evandro Chagas National Institute of Infectious Diseases from March 2013 to January 2016. It was conducted in 2 phases. The first one, a cross-sectional seroprevalence study, followed by an uncontrolled analysis of vaccine response among patients without protective antibody titers at baseline. Antibody titers to poliomyelitis were determined by microneutralization assay., Results: Among 206 SOT candidates included, 156 (76%) had protective antibody titers to all poliovirus serotypes (95% CI: 70-81%). Proven history of oral vaccination in childhood was not associated with higher seroprevalence of protective antibody. In 97% of individuals without protective antibody titers at baseline, there was adequate vaccine response with one dose of inactivated polio vaccine., Conclusions: A relevant proportion of adult candidates for SOT does not have protective titers of antibodies to one or more poliovirus serotype. One dose of inactivated vaccine elicited protective antibody titers in 97% of these subjects and should be routinely prescribed prior to SOT., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Afghanistan is one of the remaining wild-poliovirus (WPV) endemic countries. We conducted a seroprevalence survey of anti-poliovirus antibodies in Kandahar Province., Methods: Children in two age groups (6-11 months and 36-48 months) visiting Mirwais hospital in Kandahar for minor ailments unrelated to polio were enrolled. After obtaining informed consent, we collected venous blood and conducted neutralization assay to detect poliovirus neutralizing antibodies., Results: A total of 420 children were enrolled and 409/420 (97%) were analysed. Seroprevalence to poliovirus type 1 (PV1) was 97% and 100% in the younger and older age groups respectively; it was 71% and 91% for PV2; 93% and 98% for PV3. Age group (RR = 3.6, CI 95% = 2.2-5.6) and place of residence outside of Kandahar city (RR = 1.8, CI 95% = 1.2-2.6) were found to be significant risk factors for seronegativity., Conclusions: The polio eradication program in Kandahar achieved high serological protection, especially against PV1 and PV3. Lower PV2 seroprevalence in the younger age group is a result of a withdrawal of live type 2 vaccine in 2016 and is expected. Ability to reach all children with poliovirus vaccines is a pre-requisite for achieving poliovirus eradication., (Copyright © 2018 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Understanding the determinants of polio transmission and its large-scale epidemiology remains a public health priority. Despite a 99% reduction in annual wild poliovirus (WPV) cases since 1988, tackling the last 1% has proven difficult. We identified key covariates of geographical variation in polio transmission patterns by relating country-specific annual disease incidence to demographic, socio-economic and environmental factors. We assessed the relative contributions of these variables to the performance of computer-generated models for predicting polio transmission. We also examined the effect of spatial coupling on the polio extinction frequency in islands relative to larger land masses. Access to sanitation, population density, forest cover and routine vaccination coverage were the strongest predictors of polio incidence, however their relative effect sizes were inconsistent geographically. The effect of climate variables on polio incidence was negligible, indicating that a climate effect is not identifiable at the annual scale, suggesting a role for climate in shaping the transmission seasonality rather than intensity. We found polio fadeout frequency to depend on both population size and demography, which should therefore be considered in policies aimed at extinction. Our comparative epidemiological approach highlights the heterogeneity among polio transmission determinants. Recognition of this variation is important for the maintenance of population immunity in a post-polio era.

Background: Pakistan is one of only three countries where poliovirus circulation remains endemic. For the Pakistan Polio Eradication Program, identifying high risk districts is essential to target interventions and allocate limited resources., Methods: Using a hierarchical Bayesian framework we developed a spatial Poisson hurdle model to jointly model the probability of one or more paralytic polio cases, and the number of cases that would be detected in the event of an outbreak. Rates of underimmunization, routine immunization, and population immunity, as well as seasonality and a history of cases were used to project future risk of cases., Results: The expected number of cases in each district in a 6-month period was predicted using indicators from the previous 6-months and the estimated coefficients from the model. The model achieves an average of 90% predictive accuracy as measured by area under the receiver operating characteristic (ROC) curve, for the past 3 years of cases., Conclusions: The risk of poliovirus has decreased dramatically in many of the key reservoir areas in Pakistan. The results of this model have been used to prioritize sub-national areas in Pakistan to receive additional immunization activities, additional monitoring, or other special interventions.

Background: The European Region, certified polio-free in 2002, remains at risk of wild poliovirus reintroduction and emergence of circulating vaccine-derived polioviruses (cVDPV) until global polio eradication is achieved, as demonstrated by the cVDPV1 outbreak in Ukraine in 2015., Methods: We reviewed epidemiologic, clinical and virology data on cVDPV cases, surveillance and immunization coverage data, and reports of outbreak-related surveys, country missions, and expert group meetings., Results: In Ukraine, 3-dose polio vaccine coverage declined from 91% in 2008 to 15% by mid-2015. In summer, 2015, two unrelated children from Zakarpattya province were paralyzed by a highly divergent cVDPV1. The isolates were 20 and 26 nucleotide divergent from prototype Sabin strain (with 18 identical mutations) consistent with their common origin and ∼2-year evolution. Outbreak response recommendations developed with international partner support included conducting three nationwide supplementary immunization activities (SIAs) with tOPV, strengthening surveillance and implementing communication interventions. SIAs were conducted during October 2015-February 2016 (officially reported coverage, round 1-64.4%, round 2-71.7%, and round 3-80.7%). Substantial challenges to outbreak response included lack of high-level support, resistance to OPV use, low perceived risk of polio, widespread vaccine hesitancy, anti-vaccine media environment, economic crisis and military conflict. Communication activities improved caregiver awareness of polio and confidence in vaccination. Surveillance was enhanced but did not consistently meet applicable performance standards. Post-outbreak assessments concluded that cVDPV1 transmission in Ukraine has likely stopped following the response, but significant gaps in population immunity and surveillance remained., Conclusions: Chronic under-vaccination in Ukraine resulted in the accumulation of children susceptible to polioviruses and created favorable conditions for VDPV1 emergence and circulation, leading to the outbreak. Until programmatic gaps in immunization and surveillance are addressed, Ukraine will remain at high-risk for VDPV emergence and circulation, as well as at risk for other vaccine-preventable diseases., (Published by Elsevier Ltd.)

Poliovirus (PV) is the causative agent of poliomyelitis, a crippling human disease known since antiquity. PV occurs in two distinct antigenic forms, D and C, of which only the D form elicits a robust neutralizing response. Developing a synthetically produced stabilized virus-like particle (sVLP)-based vaccine with D antigenicity, without the drawbacks of current vaccines, will be a major step towards the final eradication of poliovirus. Such a sVLP would retain the native antigenic conformation and the repetitive structure of the original virus particle, but lack infectious genomic material. In this study, we report the production of synthetically stabilized PV VLPs in plants. Mice carrying the gene for the human PV receptor are protected from wild-type PV when immunized with the plant-made PV sVLPs. Structural analysis of the stabilized mutant at 3.6 Å resolution by cryo-electron microscopy and single-particle reconstruction reveals a structure almost indistinguishable from wild-type PV3.Despite the success of current vaccination against poliomyelitis, safe, cheap and effective vaccines remain sought for continuing eradication effort. Here the authors use plants to express stabilized virus-like particles of type 3 poliovirus that can induce a protective immune response in mice transgenic for the human poliovirus receptor.

No indigenous cases of poliomyelitis have occurred in the US since 1979; however the risk of importation persists until global eradication is achieved. The seropositivity rate for different age cohorts with exposures to different poliovirus vaccine types and wild virus in the US are not presently known. A convenience sample was conducted in the Kansas City metropolitan area during 2012-2103 with approximately 100 participants enrolled for each of 5 age cohorts categorized based on vaccine policy changes over time in the US. Immunization records for poliovirus vaccination were required for participants <18 y of age. We evaluated the prevalence of serum antibodies to all 3 poliovirus serotypes. Seroprevalence was evaluated by demographics as well as between polio serotypes. The overall seroprevalence to poliovirus was 90.7%, 94.4%, and 83.3%, for types 1, 2, and 3, respectively. Seroprevalence was high (88.6%-96.2%) for all 3 types of poliovirus for the 6-10 y old age group that was likely to have received a complete schedule of IPV-only vaccination. Children 2-3 y of age, who have not yet completed their full IPV series, had lower seroprevalence compared with all older age groups for types 1 and 2 (p-value <0. 05). Seroprevalence was high for all 3 types of poliovirus in the population surveyed. Seroprevalence for subjects aged 2-3 y was lower than all other age groups for serotypes 1 and 2 highlighting the importance of completing the recommended poliovirus vaccine series with a booster dose at age 4-6 y.

On August 10, 2016, 2 years after the most recent wild poliovirus (WPV) case was reported in Nigeria (in July 2014) (1), two WPV cases were reported in the northeastern state of Borno, which has been severely affected by insurgency-related insecurity since 2013. On September 9 and 26, 2016, two additional WPV cases were reported in Borno in children whose families migrated from security-compromised, inaccessible areas of the state. All four cases were WPV serotype 1 (WPV1), with genetic differences indicating prolonged undetected transmission. A large-scale emergency response plan was developed and implemented. The plan initially called for vaccination of 815,791 children during August 15-18 in five local government areas (LGAs) in the immediate vicinity of the first two WPV cases. Subsequently, the plan was expanded to regionally synchronized supplementary immunization activities (SIAs), conducted during August 27-December 6 in five Lake Chad basin countries at increased risk for national and regional WPV1 transmission (Cameroon, Central African Republic, Chad, Niger, and Nigeria). In addition, retrospective searches for missed cases of acute flaccid paralysis (AFP), enhanced environmental surveillance for polioviruses, and polio surveillance system reviews were conducted. Prolonged undetected WPV1 transmission in Borno State is a consequence of low population immunity and severe surveillance limitations associated with insurgency-related insecurity and highlights the risk for local and international WPV spread (2). Increasing polio vaccination coverage and implementing high-quality polio surveillance, especially among populations in newly secured and difficult-to-access areas in Borno and other Lake Chad basin areas are urgently needed.

Aim: To estimate the incremental net benefits (INBs) of a hypothetical ideal vaccine with all of the advantages and no disadvantages of existing oral and inactivated poliovirus vaccines compared with current vaccines available for future outbreak response., Methods: INB estimates based on expected costs and polio cases from an existing global model of long-term poliovirus risk management., Results: Excluding the development costs, an ideal poliovirus vaccine could offer expected INBs of US$1.6 billion. The ideal vaccine yields small benefits in most realizations of long-term risks, but great benefits in low-probability-high-consequence realizations., Conclusion: New poliovirus vaccines may offer valuable insurance against long-term poliovirus risks and new vaccine development efforts should continue as the world gathers more evidence about polio endgame risks.

Background: Cases of paralysis caused by poliovirus have decreased by >99% since the 1988 World Health Assembly's resolution to eradicate polio. The World Health Organization identified environmental surveillance (ES) of poliovirus in the poliomyelitis eradication strategic plan as an activity that can complement acute flaccid paralysis (AFP) surveillance. This article summarizes key public health interventions that followed the isolation of polioviruses from ES between 2012 and 2015., Methods: The grap method was used to collect 1.75 L of raw flowing sewage every 2-4 weeks. Once collected, samples were shipped at 4 °C to a polio laboratory for concentration. ES data were then used to guide program implementation., Results: From 2012 to 2015, ES reported 97 circulating vaccine-derived polioviruses (cVDPV2) and 14 wild polioviruses. In 2014 alone, 54 cVDPV type 2 cases and 1 WPV type 1 case were reported. In Sokoto State, 58 cases of AFP were found from a search of 9426 households. A total of 2 252 059 inactivated polio vaccine and 2 460 124 oral polio vaccine doses were administered to children aged <5 year in Borno and Yobe states., Conclusions: This article is among the first from Africa that relates ES findings to key public health interventions (mass immunization campaigns, inactivated polio vaccine introduction, and strengthening of AFP surveillance) that have contributed to the interruption of poliovirus transmission in Nigeria., (© 2016 World Health Organization; licensee Oxford Journals.)

The aim of this work was to coat pH-sensitive microneedle arrays with inactivated polio vaccine (IPV) particles and N-trimethyl chitosan chloride (TMC) via electrostatic interactions, and assess the immunogenicity of the vaccine after topical application of the coated microneedles in rats. The surface of 200 μm long microneedles was first chemically modified with pH-sensitive (pyridine) groups and then coated with negatively charged IPV and a positively charged polymer (TMC). To obtain a sufficient high antigen dose, 10 layers of IPV were alternately coated with TMC. The binding of IPV and TMC onto pH-sensitive microneedles was quantified and visualized by using fluorescently labeled TMC and IPV. The release of IPV and TMC from the microneedles was evaluated in ex vivo human skin by fluorescence and the immunogenicity of (unlabeled) IPV was assessed after topical application of the coated microneedles in rats. pH-sensitive microneedles were homogeneously coated with 10 layers of both IPV and TMC, resulting in 45 D antigen units IPV and 700 ng TMC per microneedle array. Fluorescence microscopy imaging revealed that both IPV and TMC were released into ex vivo human skin upon application of the coated microneedles. Finally, in vivo application of IPV-TMC-coated pH-sensitive microneedles in rats led to the induction of IPV specific antibody responses, illustrating that they are practically applicable. Topical administration of pH-sensitive microneedles coated with polyelectrolyte multinanolayers of antigens and oppositely charged polymers may be a useful approach for microneedle-based vaccination.

Background: After 25 years without poliomyelitis cases caused by circulating wild poliovirus (WPV) in Israel, sewage sampling detected WPV type 1 (WPV1) in April 2013, despite high vaccination coverage with only inactivated poliovirus vaccine (IPV) since 2005., Methods: We used a differential equation-based model to simulate the dynamics of poliovirus transmission and population immunity in Israel due to past exposure to WPV and use of oral poliovirus vaccine (OPV) in addition to IPV. We explored the influences of various immunization options to stop imported WPV1 circulation in Israel., Results: We successfully modeled the potential for WPVs to circulate without detected cases in Israel. Maintaining a sequential IPV/OPV schedule instead of switching to an IPV-only schedule in 2005 would have kept population immunity high enough in Israel to prevent WPV1 circulation. The Israeli response to WPV1 detection prevented paralytic cases; a more rapid response might have interrupted transmission more quickly., Conclusions: IPV-based protection alone might not provide sufficient population immunity to prevent poliovirus transmission after an importation. As countries transition to IPV in immunization schedules, they may need to actively manage population immunity and consider continued use of OPV, to avoid the potential circulation of imported live polioviruses before globally coordinated cessation of OPV use., (© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Oral vaccines appear less effective in children in the developing world. Proposed biologic reasons include concurrent enteric infections, malnutrition, breast milk interference, and environmental enteropathy (EE). Rigorous study design and careful data management are essential to begin to understand this complex problem while assuring research subject safety. Herein, we describe the methodology and lessons learned in the PROVIDE study (Dhaka, Bangladesh). A randomized clinical trial platform evaluated the efficacy of delayed-dose oral rotavirus vaccine as well as the benefit of an injectable polio vaccine replacing one dose of oral polio vaccine. This rigorous infrastructure supported the additional examination of hypotheses of vaccine underperformance. Primary and secondary efficacy and immunogenicity measures for rotavirus and polio vaccines were measured, as well as the impact of EE and additional exploratory variables. Methods for the enrollment and 2-year follow-up of a 700 child birth cohort are described, including core laboratory, safety, regulatory, and data management practices. Intense efforts to standardize clinical, laboratory, and data management procedures in a developing world setting provide clinical trials rigor to all outcomes. Although this study infrastructure requires extensive time and effort, it allows optimized safety and confidence in the validity of data gathered in complex, developing country settings., (© The American Society of Tropical Medicine and Hygiene.)

Poliovirus (PV), a member of the Enterovirus genus, is the etiological agent of poliomyelitis. A study carried out between 2013-2014 on 30 serum samples from acute flaccid paralysis (AFP) cases, showed a protective antibody level of 90% against poliovirus Sabin strains type 1 and type 2 and of 88% against type 3. No PV strains were isolated from 2009 to 2015 in Romania. Maintaining a high vaccine coverage level against polio is mandatory until global polio eradication, especially as the risk of polio importation remains elevated in Romania.

Background: India presented many challenges to the global effort to eliminate the transmission of wild polioviruses (WPVs) and poliomyelitis, with the last case of WPV type 2 in the world reported in northern India in 1999 and WPV types 1 and 3 circulating until early 2011., Methods: We used a differential equation-based model to characterize the dynamics of poliovirus transmission and various opportunities to increase and maintain high population immunity to poliovirus transmission for 2 high-risk areas in northern India. We explored options that India probably considered before 2011, to demonstrate the impact of strategies to accelerate WPV elimination and sustain high population immunity. We also characterized the impact of current and potential future vaccination strategies and explored the potential trade-offs associated with the various strategies., Results: National immunization policy choices impact population immunity, which leads to different numbers of expected paralytic cases and risks of circulating vaccine-derived poliovirus outbreaks. Assuming that India maintains high vaccination intensity everywhere, we do not anticipate issues with outbreaks of circulating vaccine-derived poliovirus type 2 infection following globally coordinated cessation of type 2-containting oral poliovirus vaccine use. We find a relatively modest potential role for inactivated poliovirus vaccine., Conclusions: National policy makers should consider the impacts of their vaccine choices on population immunity to poliovirus transmission., (© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Background: Poliovirus (PV) antibody seroprevalence studies assess population immunity, verify an immunization program's performance and vaccine efficacy, and guide polio eradication strategy. Namibia experienced a polio outbreak among adults in 2006, yet population seroimmunity was unknown., Methods: We tested 2061 specimens from Namibian pregnant females aged 15-44 years for neutralizing antibody to PV types 1-3 (PV1-3); all females were sampled during the 2010 National HIV Sentinel Survey. We determined the proportion of females seropositive for PV antibody by 5-year age strata, and analyzed factors associated with seropositivity, including age, gravidity, human immunodeficiency virus (HIV) infection status, residence, and antiretroviral treatment, by log-binomial regression., Results: The seroprevalence was 94.6% for PV1, 97.0% for PV2, and 85.1% for PV3. HIV-positive females had significantly lower seroprevalence than HIV-negative females for PV1 (91.8% vs 95.3%; P<.01) and PV3 (80.0% vs 86.1%; P<.01) but not for PV2 (96.4% vs 97.1%; P=.3). The prevalence ratio of seropositivity for HIV-positive females versus HIV-negative females was 0.95 (95% confidence interval [CI], .92-.98) for PV1, 0.99 (95% CI, .97-1.01) for PV2, and 0.92 (95% CI, .87-.96) for PV3., Conclusions: Despite relatively high PV seroprevalence, Namibia might remain at risk for a PV outbreak, particularly in lower-seroprevalence populations, such as HIV-positive females. Namibia should continue to maintain high routine polio vaccination coverage., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: Pockets of undervaccinated individuals continue to raise concerns about their potential to sustain epidemic transmission of vaccine-preventable diseases. Prior importations of live polioviruses (LPVs) into Amish communities in North America led to their recognition as a potential and identifiable linked network of undervaccinated individuals., Methods: We developed an individual-based model to explore the potential transmission of a LPV throughout the North American Amish population., Results: Our model demonstrates the expected limited impact associated with the historical importations, which occurred in isolated communities during the low season for poliovirus transmission. We show that some conditions could potentially lead to wider circulation of LPVs and cases of paralytic polio in Amish communities if an importation occurred during or after 2013. The impact will depend on the uncertain historical immunity to poliovirus infection among members of the community., Conclusions: Heterogeneity in immunization coverage represents a risk factor for potential outbreaks of polio if introduction of a LPV occurs, although overall high population immunity in North America suggests that transmission would remain relatively limited. Efforts to prevent spread between Amish church districts with any feasible measures may offer the best opportunity to contain an outbreak and limit its size., (© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Pakistan is one of 3 countries where transmission of indigenous wild poliovirus (WPV) has never been interrupted. Numbers of confirmed polio cases have declined by >90% from preeradication levels, although outbreaks occurred during 2008-2013. During 2012 and 2013, 58 and 93 WPV cases, respectively, were reported, almost all of which were due to WPV type 1. Of the 151 WPV cases reported during 2012-2013, 123 (81%) occurred in the conflict-affected Federally Administered Tribal Areas (FATA) and in security-compromised Khyber Pakhtunkhwa province. WPV type 3 was isolated from only 3 persons with polio in a single district in 2012. During August 2012-December 2013, 62 circulating vaccine-derived poliovirus type 2 cases were detected, including 40 cases (65%) identified in the FATA during 2013. Approximately 350 000 children in certain districts of the FATA have not received polio vaccine during supplementary immunization activities (SIAs) conducted since mid-2012, because local authorities have banned polio vaccination. In other areas of Pakistan, SIAs have been compromised by attacks targeting polio workers, which started in mid-2012. Further efforts to reach children in conflict-affected and security-compromised areas will be necessary to prevent reintroduction of WPV into other areas of Pakistan and other parts of the world., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Introduction: The objectives of this survey were to assess the seroprevalence of antibodies to poliovirus types 1 and 3 and the impact of bivalent (types 1 and 3) oral poliovirus vaccine (bOPV) use in immunization campaigns in northern India., Methods: In August 2010, a 2-stage stratified cluster sampling method identified infants aged 6-7 months in high-risk blocks for wild poliovirus infection. Vaccination history, weight and length, and serum were collected to test for neutralizing antibodies to poliovirus types 1, 2, and 3., Results: Seroprevalences of antibodies to poliovirus types 1, 2, and 3 were 98% (95% confidence interval [CI], 97%-99%), 66% (95% CI, 62%-69%), and 77% (95% CI, 75%-79%), respectively, among 664 infants from Bihar and 616 infants from Uttar Pradesh. Infants had received a median of 3 bOPV doses and 2 monovalent type 1 OPV (mOPV1) doses through campaigns and 3 trivalent OPV (tOPV) doses through routine immunization. Among subjects with 0 tOPV doses, the seroprevalences of antibodies to type 3 were 50%, 77%, and 82% after 2, 3, and 4 bOPV doses, respectively. In multivariable analysis, malnutrition was associated with a lower seroprevalence of type 3 antibodies., Conclusions: This study confirmed that replacing mOPV1 with bOPV in campaigns was successful in maintaining very high population immunity to type 1 poliovirus and substantially decreasing the immunity gap to type 3 poliovirus., (Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.)

Background: Despite intensified use of monovalent oral poliovirus type 1 vaccine and improved coverage of immunization campaigns, wild poliovirus type 1 persisted in Indian states of Uttar Pradesh and Bihar during 2006 to 2009., Methods: A serosurvey was conducted among cases of acute flaccid paralysis in the 25 high-polio-incidence districts of western Uttar Pradesh. Children were recruited by age group (6-11 months, 12-24 months, and 25-69 months) from among cases reported through the acute flaccid paralysis surveillance system between November 2008 and August 2009., Results: Seroprevalence for type 1 wild poliovirus was >96.4% for each age group. The seroprevalence of wild poliovirus types 2 and 3 increased with age, from 36.7% to 73.4% for type 2 and from 39.0% to 74.1% for type 3. In addition to the number of type-specific vaccine doses, father's level of education, being from a Muslim family, height for age, and female sex were the socioeconomic risk factors associated with seronegativity to poliovirus., Conclusions: The seroprevalence and risk factors identified in this study were consistent with the epidemiology of polio, and the findings were instrumental in optimizing vaccination strategy in western Uttar Pradesh with respect to the choice of OPV types, the frequency of supplementary immunization campaigns, and the urgency to improve routine immunization services., (© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.)

Vaccine-derived polioviruses (VDPVs) are associated with polio outbreaks and prolonged infections in individuals with primary immunodeficiencies. VDPV-specific PCR assays for each of the three Sabin oral poliovirus vaccine (OPV) strains were developed, targeting sequences within the VP1 capsid region that are selected for during replication of OPV in the human intestine. Over 2400 Sabin-related isolates and identified 755 VDPVs were screened. Sensitivity of all assays was 100%, while specificity was 100% for serotypes 1 and 3, and 76% for serotype 2. The assays permit rapid, sensitive identification of OPV-related viruses and flag programmatically important isolates for further characterization by genomic sequencing., (Published by Elsevier B.V.)

Six different adjuvants, each in combination with inactivated polio vaccine (IPV) produced with attenuated Sabin strains (sIPV), were evaluated for their ability to enhance virus neutralizing antibody titres (VNTs) in the rat potency model. The increase of VNTs was on average 3-, 15-, 24-fold with adjuvants after one immunization (serotypes 1, 2, and 3, respectively). Also after a boost immunization the VNTs of adjuvanted sIPV were on average another 7-20-27 times higher than after two inoculations of sIPV without adjuvant. The results indicate that it is feasible to increase the potency of inactivated polio vaccines by using adjuvants., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: The Global Polio Eradication Initiative, established in 1988, has made substantial progress toward achieving this target, with only 3 countries never having eliminated wild poliovirus. Persons with primary immune deficiency disorders (PIDD) exposed to OPV are at increased risk of vaccine-associated paralytic poliomyelitis (VAPP) and of prolonged excretion of Sabin polioviruses. However, the risk for prolonged excretion is not known. Therefore, we studied the prevalence of PIDD with long-term poliovirus excretion in Sri Lanka, a middle income country currently using OPV., Methods: We stimulated the referral of patients under the age of 35 years, with clinical features suggestive of immune deficiency to the single immunology clinic in the country, where these patients were investigated for the presence of PIDD. Stool samples from patients with PIDD were cultured for the presence of poliovirus (PV). Poliovirus isolates were tested for intratypic differentiation (ITD). The VP1 region of all poliovirus isolates was sequenced., Results: Of 942 patients investigated, 51 (5.4%) were diagnosed with PIDD. Five (10.2%) patients excreted poliovirus. A patient with X linked agammaglobulinemia (XLA) excreted a mixture of all three Sabin like (SL) poliovirus serotypes. One patient with severe combined immune deficiency (SCID) excreted SL type 2, and another with SCID excreted SL type 3. One patient with SCID excreted a P2 vaccine-derived poliovirus (VDPV 2), and another with common variable immune deficiency (CVID) excreted a VDPV 3. The 3 patients with SCID died before scheduled collection of subsequent samples one month later, while the patient with XLA had cleared the virus in stool sample collected after 3 and 11 months. The CVID patient with VDPV 3 excreted for 7 months, and has developed a 23 nucleotide divergence in VP1 (∼900 nucleotides) from the parental Sabin virus., Conclusions: In our study, several patients with SCID, XLA and CVID excreted poliovirus. With improving health care quality patients with CVID and XLA may survive longer especially with provision of intravenous immune globulin. Regular screening of patients with PIDD for excretion of poliovirus is necessary to identify chronic excretors and make available specific therapies., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Poliomyelitis is endemic in Northern Nigeria where there is continuous transmission of wild poliovirus 1 and 3 (WPV1 and 3) and circulating vaccine derived poliovirus 2 (cVDPV2) resulting in a high number of cases of children with acute flaccid paralysis. The seroprevalence of antibodies to polio serotypes which can be used to assess the immune status of children and the effectiveness of the vaccine against poliomyelitis is unknown, despite its endemicity in this part of the world., Objective: This study aimed to determine the seroprevalence of poliovirus antibodies in children aged 1-10 years in Zaria, Northern Nigeria., Methods: A descriptive, cross sectional, community based study was undertaken in Zaria, North Western Nigeria between 2008 and 2009. Two hundred and sixty-four (264) children aged 1-10 years were enrolled from two local government in Zaria by multistage random sampling method. Demographic data and polio immunisation history were retrieved from parents and caregivers by an interviewer administered questionnaire. Neutralising antibody titres to polioserotypes 1, 2 and 3 were assayed according to the WHO Manual for the virological investigation of polio. Antibody titres ≥ 1:8 were considered positive., Results: The mean age of the 264 children studied was 6.25 years. Fifty-five percent of the children were protected against the three polioserotypes, while 86.4%, 76.1% and 77.3% of children had neutralising antibodies to P1, P2 and P3 polioserotypes respectively. 5 (1.9%) of the children had no antibodies to all the three polioserotypes. Polio antibody seropositivity was significantly associated with higher socioeconomic status and immunisation was the single most important determinant of seropositivity to poliovirus serotypes., Conclusion: Seroprevalence to poliovirus serotypes, though higher than values found in previous studies done in Nigeria, was lower compared to findings in the developed world. The use of more immunogenic vaccines and the balanced use of OPV formulations in SIAs, with further improvements in programme quality could provide the necessary immune booster to make polio eradication in Nigeria a reality., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The widespread use of poliovirus vaccination schemes has led to a marked decline in the incidence of paralytic poliomyelitis worldwide, but wild poliovirus is still endemic in some developing countries, and in 2009 a total of 23 countries reported at least 1 case of poliomyelitis caused by wild-strain polio viruses. A serological survey was thus conducted on the immunological status against polioviruses of 318 young adults, classified by their country of origin. Immunity to poliomyelitis was assessed by neutralizing antibody titration in tissues cultured on microplates. The rate of seronegativity (≤ 1:8) in the study population was 26.7% for poliovirus type 1, 7.2% for type 2, and 22.6% for type 3. In our sample of 318 individuals, 219 (68.9%) were Italian and 99 (31.1%) were from outside the European Union (EU). The proportion of cases found seropositive to polioviruses 1 and 3 decreased significantly with older age; this age-related decrease was more evident in the Italian group than among the non-EU subjects. Any risk of the wild virus recurring and causing paralytic poliomyelitis must be prevented, keeping Europe polio free by means of appropriate immunological protection, until polio has been conclusively eradicated all over the world. Judging from our findings, it may be worth considering administering a fifth dose of polio vaccine to adolescents.

The milestone in polio eradication program is to protect effectively children aged 0-5 years against the three serotypes of poliovirus. It became necessary to measure the level of neutralizing antibodies to the three poliovirus types in an endemic State in Nigeria. Neutralizing antibodies to the poliovirus types among children aged 0-5 years was estimated using micro neutralization assay. Of 129 children, 99 (76.8%), 95 (73.6%), and 95 (73.6%) had neutralizing antibodies with the geometric mean titer of 42.7, 31.3, and 33.2 for the poliovirus type 1, 2, and 3, respectively. Fifty-three percent of the children were protected against the three types of poliovirus. Combination of poliovirus types 1 and 2, 1 and 3, and 2 and 3 were neutralized by 62.8, 58.9, and 61.2% of the children studied, respectively. Only poliovirus type 1 induced antibody titres ≥1:1,024. The number of children with neutralizing antibodies after receiving three doses was significantly higher than those who received one or two doses of oral polio vaccine (P ≤ 0.05). However, those who received more than three doses of oral polio vaccine showed no significant difference in their antibody response. The existence of immunity gap poses a risk of re-emergence of the paralytic poliovirus. The existence of unimmunized and unprotected children along with high birth rate could impede the success of polio vaccination in Nigeria. Elimination of non-compliance to polio vaccine, promotion of health education and documented evidence of vaccination of each child with the parents may facilitate the success of polio eradication program in Nigeria., (Copyright © 2012 Wiley Periodicals, Inc.)

Since the resolution of the World Assembly in 1988 to eradicate polio globally, substantial progress toward this target has been achieved, but the final goal remains elusive. India and other tropical developing countries present a unique challenge because of the much lower oral poliovirus vaccine (OPV) immunogenicity compared to industrialized countries, both in terms of humoral and mucosal immunity. To overcome this challenge, further research is needed to elucidate the causes for the suboptimal OPV immunogenicity, better defining the optimal vaccine schedules and delivery strategies, developing and evaluating adjuvants to boost OPV immunogenicity, and improving the methods for directly measuring mucosal immunity., (Copyright © 2011 World Health Organization. Published by Elsevier Ltd.. All rights reserved.)

Background: This study is based on EPI (Expanded Program on Immunization) immunization surveys and surveillance of polio, its challenges in immunization and the way forward to overcome these challenges., Methods: Several Government documents, survey reports and unpublished program documents were studied and online search was made to find information on EPI Pakistan. SPSS 16 and Microsoft Excel 2007 were used for the statistical analysis., Results: Immunization against polio is higher in urban areas as compared to rural areas. Marked variation in vaccination has been observed in different provinces of Pakistan in the last decade. Secondly 10-20% of the children who have received their first dose of trivalent polio vaccine were deprived of their 2nd and 3rd dose because of poor performance of EPI and Lack of information about immunization., Conclusion: In spite of numerous successes, such as the addition of new vaccines and raising immunization to over 100% in some areas, EPI is still struggling to reach its polio eradication goals. Inadequate service delivery, lack of information about immunization and limited number of vaccinators were found to be the key reason for poor performance of immunization and for large number of cases reported each year due to the deficiency of second and third booster dose.

On November 4, 2010, the Republic of the Congo declared a poliomyelitis outbreak. A cross-sectional survey in Pointe-Noire showed poor sanitary conditions and low vaccination coverage (55.5%), particularly among young adults. Supplementary vaccination should focus on older age groups in countries with evidence of immunity gaps.

The Global Polio Eradication Initiative (GPEI) was launched in 1988. By 2006, transmission of indigenous wild poliovirus (WPV) was interrupted in all but four countries (Afghanistan, Pakistan, India, and Nigeria). Subsequently, 39 previously polio-free countries experienced outbreaks following importation of WPV, and transmission became reestablished in Angola, Chad, Democratic Republic of the Congo (DRC), and Sudan. This update summarizes progress toward polio eradication during 2010 and the first quarter of 2011. Worldwide, 1,291 WPV cases were reported in 2010, a 19% decrease from 2009; WPV type 3 (WPV3) cases decreased 92%, but WPV type 1 (WPV1) cases increased 145%. During 2010, 232 (18%) WPV cases were reported from the four polio-endemic countries; 159 (12%) cases were reported in Angola, Chad, and DRC; and 900 (70%) cases were reported in 13 countries, including two countries with outbreaks continuing from 2009 and 11 with new importations. During 2010, WPV cases in India and Nigeria decreased ≥94% compared with 2009. Outbreaks in Tajikistan and the Republic of the Congo (Congo) accounted for two thirds of cases (842) in 2010. All new outbreaks in 11 polio-free countries in 2010 were stopped or were on track to being stopped within 6 months of outbreak confirmation. During January--March 2011, substantially more WPV cases occurred in Chad, DRC, and Pakistan than during the same period of 2010. To further progress toward polio eradication and achieve the 2012 target of ending all WPV transmission, significant increases in resources and political commitment are needed.

During replication, oral polio vaccine (OPV) can revert to neurovirulence and cause paralytic poliomyelitis. In individual vaccinees, it can acquire specific revertant point mutations, leading to vaccine-associated paralytic poliomyelitis (VAPP). With longer replication, OPV can mutate into vaccine-derived poliovirus (VDPV), which causes poliomyelitis outbreaks similar to those caused by wild poliovirus. After wild poliovirus eradication, safely phasing out vaccination will likely require global use of inactivated polio vaccine (IPV) until cessation of OPV circulation. Mexico, where children receive routine IPV but where OPV is given biannually during national immunization days (NIDs), provides a natural setting to study the duration of OPV circulation in a population primarily vaccinated with IPV. We developed a real-time PCR assay to detect and distinguish revertant and nonrevertant OPV serotype 1 (OPV-1), OPV-2, and OPV-3 from RNA extracted directly from stool and sewage. Stool samples from 124 children and 8 1-liter sewage samples from Orizaba, Veracruz, Mexico, collected 6 to 13 weeks after a NID were analyzed. Revertant OPV-1 was found in stool at 7 and 9 weeks, and nonrevertant OPV-2 and OPV-3 were found in stool from two children 10 weeks after the NID. Revertant OPV-1 and nonrevertant OPV-2 and -3 were detected in sewage at 6 and 13 weeks after the NID. Our real-time PCR assay was able to detect small amounts of OPV in both stool and sewage and to distinguish nonrevertant and revertant serotypes and demonstrated that OPV continues to circulate at least 13 weeks after a NID in a Mexican population routinely immunized with IPV.

Wild poliovirus has remained endemic in northern Nigeria because of low coverage achieved in the routine immunization program and in supplementary immunization activities (SIAs). An outbreak of infection involving 315 cases of type 2 circulating vaccine-derived poliovirus (cVDPV2; >1% divergent from Sabin 2) occurred during July 2005-June 2010, a period when 23 of 34 SIAs used monovalent or bivalent oral poliovirus vaccine (OPV) lacking Sabin 2. In addition, 21 "pre-VDPV2" (0.5%-1.0% divergent) cases occurred during this period. Both cVDPV and pre-VDPV cases were clinically indistinguishable from cases due to wild poliovirus. The monthly incidence of cases increased sharply in early 2009, as more children aged without trivalent OPV SIAs. Cumulative state incidence of pre-VDPV2/cVDPV2 was correlated with low childhood immunization against poliovirus type 2 assessed by various means. Strengthened routine immunization programs in countries with suboptimal coverage and balanced use of OPV formulations in SIAs are necessary to minimize risks of VDPV emergence and circulation.

On November 4, 2010, a case of wild poliovirus type 1 (WPV1) was confirmed in a resident of the port city, Pointe Noire, the first WPV case in Republic of the Congo (ROC) in 10 years. The WPV1 isolate from this resident was genetically most closely related to WPV1 isolated in Angola in 2010. Subsequent investigation, including active case finding, revealed increased acute flaccid paralysis (AFP) hospital admissions beginning in September. Weekly admissions rose from approximately 10 AFP patients in early October to approximately 80 by the end of October and November. With response immunization activities, weekly AFP admissions fell to fewer than five by the end of December. A provisional total of 554 AFP cases were identified nationally, with paralysis onset from September 20, 2010, to February 27, 2011; 374 (68%) of the AFP cases were among males. Overall, 465 (84%) AFP cases were among residents of the neighboring departments of Kouilou and Pointe Noire, where the outbreak apparently began and where approximately 21% of ROC's 4.2 million persons reside. The case-fatality rate (CFR) in Kouilou and Pointe Noire was 40% (187 deaths of 465 cases), compared with 11% (10 of 89) elsewhere in ROC. Additionally, the median age of patients with AFP in Kouilou and Pointe Noire was 20 years (range: 0-63 years), compared with 7.5 years (range: 1-68 years) elsewhere in ROC.

In this study, the serological status of the southern Greek population in the 1–10-year, 11–20-year, 21–30-year and 31–40-year age groups with regard to Sabin vaccine strains and a collection of 15 recombinant and four non-recombinant poliovirus vaccine strains was determined. For all three poliovirus types, the highest neutralization test (NT) titres were observed in the 1–10- year age group, indicating a good response to vaccination. In general, the serological status of the population of southern Greece with regard to poliovirus is better for types 1 and 2 than for type 3. The presence of the lowest NT titre in the 21– 30-year age group against poliovirus type 3 suggests the need for a booster dose of monovalent Sabin3 vaccine to ensure personal and herd immunity.

A blocking-ELISA procedure was used to quantify antibodies in sera of humans immunized with poliovirus vaccines. Titers determined by this method demonstrated an excellent correlation with the results of neutralization test. Testing of serum potency with a panel of type 1 poliovirus strains altered antigenically was used to evaluate the composition of polyclonal sera with respect to the epitope specificity of constituent antibodies. Paratope profiles of various polyclonal sera determined by this new method differed, depending on the type of vaccine used for immunization. Antibodies induced in response to inactivated poliovirus vaccine (IPV) contained antibodies directed primarily against antigenic site 1, while sera from recipients of the oral poliovirus vaccine (OPV) contained antibodies to site 3. Antibodies to antigenic sites 2 and 4 were minor constituents in both types of sera. Pre-immunization sera had paratope profiles similar to OPV-induced antisera, allowing the discrimination between antibodies induced by IPV and maternal antibodies. The new method may be useful for analyzing results of clinical trials and to compare immunity induced by different poliovirus vaccines., (Published by Elsevier B.V.)