Declaración SLIPE: Aumento de la cobertura antipoliomielítica con vacunas más seguras: una urgencia inaplazable en Latinoamérica / SLIPE Declaration: Increasing anti-polio coverage with safer vaccines: an urgent need that cannot be postponed in Latin America

Ante el riesgo real de ocurrencia de brotes de parálisis fláccida aguda en la región debidos a poliovirus derivado de la vacuna Sabin o a la importación de poliovirus salvaje, la Sociedad Latinoamericana de Infectología Pediátrica comisionó a un grupo ad hoc de expertos integrantes del Comité de Vacunas y Biológicos de la institución, para redactar un documento oficial de posición sobre la necesidad imperiosa de incrementar los niveles de inmunización contra la enfermedad en la región e incorporar definitivamente en forma exclusiva la vacuna de polio inactivada en todos los esquemas nacionales de vacunación. La presente publicación discute las principales conclusiones y recomendaciones generadas como resultado de esta actividad.

Given the actual risk of poliomyelitis outbreaks in the region due to poliovirus derived from the Sabin vaccine or the importation of wild poliovirus, the Latin American Society of Pediatric Infectious Diseases commissioned an ad hoc group of experts from the institution's Vaccines and Biologicals Committee, to draft an official position paper on the urgent need to increase immunization levels against the disease in the region and incorporate inactivated polio vaccine exclusive schedules in all national immunization programs. This publication discusses the main conclusions and recommendations generated as a result of such activity.

Increasing polio coverage with safer vaccines: a pressing need in Latin America

Given the actual risk of poliomyelitis outbreaks in the region due to poliovirus derived from the Sabin vaccine or the importation of wild poliovirus, the Latin American Society of Pediatric Infectious Diseases commissioned an ad hoc group of experts from the institution's Vaccines and Biologicals Committee, to draft an official position paper on the urgent need to increase immunization levels against the disease in the region and incorporate inactivated polio vaccine exclusive schedules in all national immunization programs. This publication discusses the main conclusions and recommendations generated as a result of such activity.

Ante el riesgo real de ocurrencia de brotes de parálisis fláccida aguda en la región debidos a poliovirus derivado de la vacuna Sabin o a la importación de poliovirus salvaje, la Sociedad Latinoamericana de Infectología Pediátrica comisionó a un grupo ad hoc de expertos integrantes del Comité de Vacunas y Biológicos de la institución, para redactar un documento oficial de posición sobre la necesidad imperiosa de incrementar los niveles de inmunización contra la enfermedad en la región e incorporar definitivamente en forma exclusiva la vacuna de polio inactivada en todos los esquemas nacionales de vacunación. La presente publicación discute las principales conclusiones y recomendaciones generadas como resultado de esta actividad.

SV40 seroprevalence in two Latin American countries involved in field trials of candidate oral poliovaccines.

OBJECTIVES: This study sought to determine SV40 seroprevalence in residents of two Latin American countries, Colombia and Nicaragua, which were sites of prelicensure oral poliovaccine (OPV) trials. METHODS: Archival sera were tested for SV40 neutralizing antibody using a virus-specific plaque-reduction assay. Samples included 517 sera from Colombia and 149 sera from Nicaragua. RESULTS: Overall SV40 seroprevalence was 22.8% for Colombian subjects and 12.8% for Nicaraguans. Subgroups of Colombian subjects ranged in frequency of SV40 seropositivity from 10.0% to 38.6%. Birth cohorts both older and younger than the age cohort that contained potential OPV vaccinees from both countries had SV40 antibodies. Gender and ethnicity had no significant effects on SV40 seropositivity. CONCLUSIONS: Inhabitants of both Colombia and Nicaragua had detectable SV40 neutralizing antibody, including those of ages presumably not recipients of potentially SV40-contaminated OPV. This observation provides support for the concept that transmission of SV40 human infections can occur. Frequency of SV40 antibody positivity was elevated over that reported for the US where there was limited use of contaminated OPV. This investigation indicates also that study results of SV40 infections in humans will reflect whether subject populations had probable exposures to contaminated poliovaccines and to environmental conditions favoring cycles of viral transmission.

Remarks on the possibility of introducing the fractionated dose of the inactivated poliomyelitis vaccine in the Latin American Child Immunization Schedule

Abstract Given that the last notified case of poliomyelitis due to wild poliovirus type 2 was in 1999, in 2012, the Strategic Advisory Group of Experts on Immunization (SAGE) of the World Health Organization (WHO) recommended the withdrawal of the type 2 component of oral polio vaccine (OPV) and the introduction of a bivalent OPV (bOPV) in all countries by 2016. WHO recommended also that the withdrawal should be preceded by the introduction of at least one dose of inactivated poliovirus vaccine (IPV) in routine immunization schedules. The introduction of IPV prior to the change of the bOPV in 2016 to trivalent OPV (tOPV) was based on the concept of ensuring that a substantial proportion of the population would be protected against type 2 polio after the removal of the type 2 OPV. However, the world's two producers of IPV (Bilthoven Biologicals and Sanofi) have faced problems in the production of this vaccine and therefore reported a reduction of the global supply of IPV. In response to the potential shortage of IPV, at a meeting held on March 10 2017, the SAGE and Technical Advisory Group (TAG) of the Pan American Health Organization (PAHO) urged the countries in the Latin American region to replace the routine administration of the full doses of inactivated polio vaccine (IPV-C) in the immunization schedule (administered by intramuscular route), administering a fraction of the full dose in two intradermal shots (IPV-f). The possibility of this strategy was analyzed by opinion leaders convened by the Paraguayan Society of Pediatrics with the support of the Latin American Society of Pediatric Infectious Diseases (SLIPE) and Latin American Association of Pediatrics (ALAPE). This document presents the results of the discussion.

Consideraciones referente a la posibilidad de introducir la dosis fraccionada de la vacuna antipoliomielitis inactivada en el calendario de Inmunizaciones del Niño Latinoamericano / Remarks on the possibility of the introduction of fractionated dose of the inactivated poliomyelitis vaccine in the Latin American Child Immunization Schedule

As last notified case of poliomyelitis due to wild poliovirus type 2 was 1999, in 2012, the Strategic Advisory Group of Experts on Immunization (SAGE) of the World Health Organization (WHO) recommended the withdrawal of the type 2 component of oral polio vaccine (OPV) and the introduction of bivalent OPV (bOPV) in all countries by 2016. WHO recommended also that the withdrawal should be preceded by the introduction of at least one dose of inactivated poliovirus vaccine (IPV) in routine immunization schedules. The introduction of IPV prior to the change of the bOPV in 2016 to trivalent OPV (tOPV) was based on the concept of ensuring that a substantial proportion of the population would be protected against type 2 polio after the removal of the type 2 OPV. However, the world's two producers of IPV (Bilthoven Biologicals and Sanofi) have faced problems in the production of this vaccine and therefore reported reduction in IPV global supply. In response to the possible shortage of IPV, the SAGE and Technical Adviser Group (TAG) of the Pan American Health Organization (PAHO), in the meeting of March 10, 2017, has urged that countries in the Latinamerican region should replace the routine administration of the full doses of polio inactivated vaccine (IPV-C) in the immunization schedule (administered by intramuscular route) by the administration of a fraction of the full dose in two shots by intradermal route (IPV-f). The possibility of this strategy was analyzed by leaders of opinions gathered by the call of the Paraguayan Pediatric Society with the support of the Latin American Society of Pediatric Infectious Diseases (SLIPE) and Latin American Association of Pediatrics (ALAPE). The results of the discussion are presented in this document.

Clearing Vaccine-Derived Poliovirus Infection Following Hematopoietic Stem Cell Transplantation: a Case Report and Review of Literature.

The use of oral poliovirus vaccine in a worldwide scale has led to a 99.9% decrease in annual incidence of wild-type poliomyelitis and the eradication of serotype 2 poliovirus. However, the emergence of vaccine-derived polioviruses (VDPVs) is endangering the eradication program. Patients with combined immunodeficiencies are at increased risk of both vaccine-associated poliomyelitis and prolonged asymptomatic infection with immunodeficiency-associated VDPVs (iVDPVs). Herein, we present a severe combined immunodeficiency patient with prolonged and asymptomatic iVDPV infection. He continued to shed poliovirus during immunoglobulin replacement therapy and cleared the infection following successful hematopoietic stem cell transplantation (HSCT). To explain the efficiency of HSCT in clearing the infection, we reviewed the literature for all reports of HSCT in iVDPV-excreting patients and discussed novel ideas about the role of different immune mechanisms, including cell-mediated interactions, in mounting immune responses against poliovirus infections. This study could provide further insights into the immune mechanisms contributing to the clearance of enteroviral infections.

Vaccine-associated paralytic poliomyelitis in a patient with acute lymphocytic leukemia.

We report a case of vaccine-associated paralytic poliomyelitis (VAPP) in an immunocompromised patient with acute lymphocytic leukemia who was initially diagnosed with aseptic meningitis. Isolation of Sabin-like type 1 poliovirus from the patient's cerebrospinal fluid made this a case of vaccine-related poliovirus (VRPV) infection. The patient developed paralysis and respiratory distress and deceased a few months after onset of paralysis with respiratory failure. This tragic case report highlights the emergence of VAPP and indicates the importance of timely diagnosis of VRPV infections to improve clinical management of VRPV-infected patients and to prevent the devastating consequences of silent introduction of VRPVs in treatment wards and eventually in the society.

Vaccine-related poliovirus shedding in trivalent polio vaccine and human immunodeficiency virus status: analysis from under five children.

BACKGROUND: Poliomyelitis is an acute viral infection caused by poliovirus and transmitted via the fecal-oral route. The causative agent is one of the three serotypes of poliovirus (serotypes 1, 2, 3) that differ slightly in capsid protein. Prolonged vaccine-related poliovirus shedding in human immunodeficiency virus (HIV) positive individuals has been linked to possible reservoir for reintroduction of polioviruses after eradication. The study therefore aimed at estimating the duration for vaccine-related poliovirus shedding among potentially and HIV-infected persons. METHODS: Poliovirus excretion was studied following vaccination of children aged ≤ 59 month per human immunodeficiency virus status after national immunization days. Their medical records were reviewed to identify the child's HIV status, demographic and immunization data. Sequential stool samples were collected at site 2nd, 4th and 8th week after trivalent oral poliovirus vaccine (tOPV) was administered. To isolate suspected polioviruses and non-polio enteroviruses, characterize poliovirus subtypes by intratypic differentiation and Sabin vaccine derived poliovirus, real time polymerase chain reaction was applied. Shedding for ≥ 24 weeks was defined as long-term persistence. RESULTS: The mean age of the study population was 28.6 months, while the median age was 24 months. Of the children recruited, majority were in the 25-48 months (n = 12; 46.2%) age category. All the HIV-positive children (n = 10) had mild symptomatic HIV status and did shed vaccine-related polioviruses between weeks 2 and 4 respectively. No participant shed polioviruses for ≥ 6 weeks. CONCLUSIONS: It was evident mildly symptomatic HIV+ children sustain the capacity to clear vaccine-related poliovirus. The oral poliovirus vaccine-2 (Sabin like) that was detected in one HIV-infected child's stool 6 weeks after the national immunization days was predominantly non revertant. There was no evident prolonged poliovirus shedding among the participants enlisted in the present study. High powered studies are desired to further corroborate these findings.

Comprehensive screening for immunodeficiency-associated vaccine-derived poliovirus: an essential oral poliovirus vaccine cessation risk management strategy.

If the world can successfully control all outbreaks of circulating vaccine-derived poliovirus that may occur soon after global oral poliovirus vaccine (OPV) cessation, then immunodeficiency-associated vaccine-derived polioviruses (iVDPVs) from rare and mostly asymptomatic long-term excretors (defined as ⩾6 months of excretion) will become the main source of potential poliovirus outbreaks for as long as iVDPV excretion continues. Using existing models of global iVDPV prevalence and global long-term poliovirus risk management, we explore the implications of uncertainties related to iVDPV risks, including the ability to identify asymptomatic iVDPV excretors to treat with polio antiviral drugs (PAVDs) and the transmissibility of iVDPVs. The expected benefits of expanded screening to identify and treat long-term iVDPV excretors with PAVDs range from US$0.7 to 1.5 billion with the identification of 25-90% of asymptomatic long-term iVDPV excretors, respectively. However, these estimates depend strongly on assumptions about the transmissibility of iVDPVs and model inputs affecting the global iVDPV prevalence. For example, the expected benefits may decrease to as low as US$260 million with the identification of 90% of asymptomatic iVDPV excretors if iVDPVs behave and transmit like partially reverted viruses instead of fully reverted viruses. Comprehensive screening for iVDPVs will reduce uncertainties and maximize the expected benefits of PAVD use.

Contribution of polio eradication initiative to effective new vaccine introduction in Africa, 2010-2015.

BACKGROUND: Significant progress has been made to increase access to vaccines in Africa since the 1974 launch of the Expanded Programme on Immunization (EPI). Successes include the introduction of several new vaccines across the continent and likely eradication of polio. We examined the contribution of polio eradication activities (PEI) on new vaccine introduction in the countries of the African Region. METHODS: We reviewed country specific PEI reports to identify best practices relevant to new vaccine introduction (NVI), and analyzed trends in vaccine coverage during 2010-2015 from immunization estimates provided by WHO/UNICEF. RESULTS: Of the 47 countries in African Region 35 (74%) have introduced PCV, 27 (57%) have introduced rotavirus, and 14 (30%) have introduced IPV. National introductions for HPV vaccine have been done in 5 countries, while 15 countries have held demonstration and pilot projects. In 2014, the regional coverage for the third dose of PCV (PCV3) and rotavirus vaccines was 50% and 30% respectively. By end of 2015, all countries within the meningitis belt will have introduced MenAfriVac™ vaccine. CONCLUSIONS: PEI activities had a positive effect in strengthening the process of new vaccine introduction in the African Region. The major contribution was in availing immunization funding and providing trained and experienced technical staff to introduce vaccines. More investment is needed to advocate and sustain funding levels to maintain the momentum gained in introducing new vaccines in the region.

Association of CMV, HBV, or HCV co-infection with vaccine response in adults with well-controlled HIV infection.

Even after CD4 count recovery on antiretroviral therapy, HIV infection is associated with decreased response to most vaccines compared to the general population. Chronic infections with viruses such as cytomegalovirus (CMV), hepatitis B virus (HBV), and hepatitis C virus (HCV), which are more prevalent in HIV-infected populations, have been linked to immune dysfunction and decreased vaccine response in the general population. However, whether co-infection with these other viruses contributes to the decreased vaccine response seen in adults with well-controlled HIV infection is unknown. We conducted a secondary analysis of data and serum from adults with well-controlled HIV infection from an inactivated polio vaccine trial (224 subjects) and a pneumococcal conjugate vaccine study (128 subjects). We evaluated the association of CMV, HBV, or HCV co-infection with post-vaccination antibody levels using both univariate and multivariate analyses, controlling for factors such as age, race, CD4 count, comorbidities, smoking status, and baseline antibody levels. Ninety-three percent, 7%, and 14% of subjects were co-infected with CMV, HBV, and HCV respectively. On both univariate and multivariate analysis, neither CMV nor HCV co-infection were significantly associated with post-vaccination antibody levels to either vaccine. HBV co-infection was significantly associated with post-vaccination antibody concentrations for pneumococcal serotype 7F on univariate analysis and 6A on multivariate analysis, but the association was with higher antibody concentrations. In conclusion, co-infection with CMV, HBV, or HCV does not appear to contribute to the decreased vaccine response seen in adults with well-controlled HIV infection.

Screening for long-term poliovirus excretion among children with primary immunodeficiency disorders: preparation for the polio posteradication era in Bangladesh.

BACKGROUND: Persons with primary immune deficiency disorders (PIDD) who receive oral poliovirus vaccine (OPV) may transmit immunodeficiency-associated vaccine-derived polioviruses (iVDPVs) and cause paralytic polio. The objective of this study was to identify children with PIDD in Bangladesh, and estimate the proportion with chronic poliovirus excretion. METHODS: Patients admitted at 5 teaching hospitals were screened for PIDD according to standardized clinical case definitions. PIDD was confirmed by age-specific quantitative immunoglobulin levels. Stool specimens were collected from patients with confirmed PIDD. RESULTS: From February 2011 through January 2013, approximately 96 000 children were screened, and 53 patients were identified who met the clinical case definition for PIDD. Thirteen patients (24%) had age-specific quantitative immunoglobulins results that confirmed PIDD. Of these, 9 (69%) received OPV 3-106 months before stool specimen collection. Among 11 patients, stool specimens from 1 patient tested positive for polioviruses 34 months after OPV ingestion. However, the poliovirus isolate was not available for genetic sequencing, and a subsequent stool specimen 45 days later was negative. CONCLUSIONS: The risk of chronic poliovirus excretion among children with PIDD in Bangladesh seems to be low. The national polio eradication program should incorporate strategies for screening for poliovirus excretion among patients with PIDD.

Immunity against poliomyelitis in the Netherlands, assessed in 2006 to 2007: the importance of completing a vaccination series.

Europe has been declared polio-free since 2002. Here we describe the seroprotection against poliomyelitis in the Dutch population using banked serum samples. Samples from 1,581 inhabitants of eight municipalities with low vaccination coverage (LVC) and an additional 6,386 samples from a nationwide (NS) group (clinical trial number: ISRCTN20164309; collected in 2006­07) were tested for neutralising antibodies (log² reciprocal titres (GMT); non-protection <3) against all three poliomyelitis serotypes. Demographic and epidemiological data were used for statistical regression analysis. Seroprevalence in the NS was 94.6% (type 1), 91.8% (type 2) and 84.0% (type 3). Infants (0­7 months-old) had ≥80% seroprevalence for all serotypes. The highest seroprevalence was found in children, with type 1 and type 2 in five year-olds and type 3 in nine to 10 year-olds. In the LVC group, orthodox protestants, many of whom refuse vaccination, showed seroprevalence rates of 64.9% (type 1), 61.0% (type 2) and 62.1% (type 3). In the NS group, non-Western immigrants and travellers to non-European continents had higher seroprevalences compared to Western immigrants and travellers within Europe, respectively. The Dutch National Immunisation Programme against poliomyelitis has provided good seroprotection, with high and long-lasting GMTs against all serotypes upon completion. The unvaccinated population remains at risk.

Impacto económico de la introducción de la vacuna inactivada inyectable contra la poliomielitis en Colombia / Economic impact of introducing the injectable inactivated polio vaccine in Colombia

OBJETIVOS: Evaluar la relación costo-efectividad de la introducción de la vacuna inyectable contra la poliomielitis (VIP) en Colombia con respecto al sistema actual basado en el empleo de la vacuna oral (VOP). MÉTODOS: Se diseñó un modelo de Markov basado en una cohorte hipotética de recién nacidos que recibiría la VIP o la VOP con un seguimiento de dos años y estimaciones mensuales del número de casos de poliomielitis paralítica asociada con la vacuna (PPAV). El análisis del costo se realizó desde la perspectiva del asegurador (costos a lo largo de la vida) y la sociedad (casos de PPAV evitados y años de vida ajustados por discapacidad [AVAD] evitados). RESULTADOS: Entre 1988 y 1998 se aplicaron en Colombia 22,5 millones de dosis de la VOP y se detectaron nueve casos de PPAV, para una tasa de 4,0 ¥ 10-7 por dosis. Según el modelo, se podrían esperar entre 2 y 4 casos de PPAV en los dos años de seguimiento. El costo de tratar los casos de PPAV sería de US$ 302 008, con costos de vacunación con la VOP de US$ 737 037 y de US$ 5 527 777 con la VIP. La vacunación con la VIP permitiría evitar 64 AVAD con un costo de US$ 71 062 por AVAD evitado; evitar un caso de PPAV mediante la sustitución de la VOP por la VIP costaría entre US$ 1,8 millones y US$ 2,2 millones. CONCLUSIONES: La sustitución de la VOP por la VIP no es una medida efectiva en función del costo en Colombia, incluso si se sustituyera la vacuna celular contra la tos ferina, actualmente en uso, por una vacuna acelular combinada con una VIP.

OBJECTIVE: Evaluate the cost-effectiveness of introducing the injectable inactivated polio vaccine (IPV) in Colombia versus the current system based on the use of the oral vaccine (OPV). METHODS: A Markov model was designed, based on a hypothetical cohort of newborns that would receive the IPV or the OPV vaccine, with a two-year follow-up and monthly estimates of the number of cases of vaccine-associated paralytic poliomyelitis (VAPP) that would emerge. The cost was analyzed from the perspective of the insurer (costs throughout life) and society (cases of VAPP and disability-adjusted life years [DALYs] prevented). RESULTS: From 1988 to 1998, some 22.5 million doses of OVP were administered in Colombia and nine cases of VAPP were detected, for a rate of 4.0 ¥ 10-7 dose. According to the model, 2 to 4 cases of VAPP could be anticipated in the following two years. The cost of treating the VAPP cases would total US$302 008, with the cost of vaccination with OPV coming to US$737 037 and with IPV, US$5 527 777. Vaccination with IPV would prevent 64 DALYs, at a cost of US$71 062 per DALY prevented; preventing one case of VAPP by substituting OPV with IPV would cost between US$1.8 and US$2.2 million. CONCLUSIONS: Substituting OPV with IPV is not a cost-effective measure in Colombia, even if the cellular vaccine against whooping cough currently in use were replaced with an acellular vaccine combined with an IPV.

Vacunación antipoliomielítica en niños de la Ciudad de Buenos Aires / Antipoliomyelitic vaccination in children living in Buenos Aires City

A raíz de la presentación de un caso confirmado de poliomielitis paralítica por virus Sabin derivado (VSD) en niños de 15 meses se analizó la cobertura de vacunación antipoliomielítica en niños residentes en la Ciudad de Buenos Aires, durante el trienio 2006/2008. Se observó una mejora a lo largo del período analizado, pero sólo hubo valores superiores al 95 por ciento para la primera dosis. Aumentó la proporción de vacuna inactivada (IPV) en desmedro de la vacuna oral viva (OPV); en 2008, la cobertura con IPV primera dosis fue del 37,64 por ciento y del 19,48 por ciento para el ingreso escolar. La falta de inmunidad intestinal que se presenta en los niños vacunados con IPV, asociada a coberturas insatisfactorias condiciona un terreno propicio para la circulación de virus salvaje o VSD, lo cual favorece la aparición de casos de poliomielitis paralítica en niños no vacunados o inmunodeficientes.

Comparison of poliovirus recombinants: accumulation of point mutations provides further advantages.

The roles of recombination and accumulation of point mutations in the origin of new poliovirus (PV) characteristics have been hypothesized, but it is not known which are essential to evolution. We studied phenotypic differences between recombinant PV strains isolated from successive stool specimens of an oral PV vaccine recipient. The studied strains included three PV2/PV1 recombinants with increasing numbers of mutations in the VP1 gene, two of the three with an amino acid change I-->T in the DE-loop of VP1, their putative PV1 parent and strains Sabin 1 and 2. Growth of these viruses was examined in three cell lines: colorectal adenocarcinoma, neuroblastoma and HeLa. The main observation was a higher growth rate between 4 and 6 h post-infection of the two recombinants with the I-->T substitution. All recombinants grew at a higher rate than parental strains in the exponential phase of the replication cycle. In a temperature sensitivity test, the I-->T-substituted recombinants replicated equally well at an elevated temperature. Complete genome sequencing of the three recombinants revealed 12 (3), 19 (3) and 27 (3) nucleotide (amino acid) differences from Sabin. Mutations were located in regions defining attenuation, temperature sensitivity, antigenicity and the cis-acting replicating element. The recombination site was in the 5' end of 3D. In a competition assay, the most mutated recombinant beat parental Sabin in all three cell lines, strongly suggesting that this virus has an advantage. Two independent intertypic recombinants, PV3/PV1 and PV3/PV2, also showed similar growth advantages, but they also contained several point mutations. Thus, our data defend the hypothesis that accumulation of certain advantageous mutations plays a key role in gaining increased fitness.

Molecular analysis and implications of neurovirulent circulating vaccine-derived poliovirus in Jamaica: a case report and review of literature / Análisis molecular e implicaciones del poliovirus derivado de las vacunas neurovirulentas circulantes (reporte de un caso y revisión de la literatura)

As the goal to eradicate wild polio virus (WPV) is approached, outbreaks associated with vaccine derived polioviruses (VDPV) with neurovirulent properties have emerged. The relevance for the spread of infection by nonparalytic cVDPV cases, with mutations associated with neurovirulence, is discussed with reference to the molecular analysis of a VDPV isolated from a Jamaican child who presented with aseptic meningitis. Potential risks to the Jamaican community resulting from circulation of cVDPV, and critical factors defined by the World Health Organization (WHO) in the global eradication of Polio are analyzed in the context of immunization coverage, and the need to stop all Oral Polio Vaccine (OPV) use once wild polioviruses (WPVs) have been eradicated.

A medida que nos hemos acercado a la meta de erradicar el virus de la polio salvaje (VPS), se han producido brotes asociados con los poliovirus derivados de la vacuna (VDPV) con propiedades neurovirulentas. El presente trabajo discute la importancia de estos en la diseminación de la infección por casos no paralíticos de cVDPV, en relación con el análisis molecular de un VDPV aislado a partir de un niño jamaicano que presentaba meningitis aséptica. Los riesgo potenciales para la comunidad jamaicana como resultado de la circulación de cVDPV, y los factores críticos definidos por la Organización de Mundial de la Salud (OMS) en la erradicación global de la polio, se analizan en el contexto de la cobertura de la inmunización, y la necesidad de detener todo uso de la Vacuna Oral de la Polio (VOP), una vez que los poliovirus salvajes (PVS) hayan sido erradicados.

Impact of exogenous sequences on the characteristics of an epidemic type 2 recombinant vaccine-derived poliovirus.

Pathogenic circulating vaccine-derived polioviruses (cVDPVs) have become a major obstacle to the successful completion of the global polio eradication program. Most cVDPVs are recombinant between the oral poliovirus vaccine (OPV) and human enterovirus species C (HEV-C). To study the role of HEV-C sequences in the phenotype of cVDPVs, we generated a series of recombinants between a Madagascar cVDPV isolate and its parental OPV type 2 strain. Results indicated that the HEV-C sequences present in this cVDPV contribute to its characteristics, including pathogenicity, suggesting that interspecific recombination contributes to the phenotypic biodiversity of polioviruses and may favor the emergence of cVDPVs.