Vaccine-derived Poliovirus Type Research Articles

Field Monitoring of the Implementation of Polio Supplementary Immunization Activities Following Circulating Vaccine-Derived Polio Virus Type 2 (CVDPV2) Outbreak in Aceh, Indonesia

Field Monitoring of the Implementation of Polio Supplementary Immunization Activities Following Circulating Vaccine-Derived Polio Virus Type 2 (CVDPV2) Outbreak in Aceh, Indonesia

Poliomyelitis Outbreak in Papua New Guinea, 2018

Objective: Vaccine-derived poliovirus (VDPV) remains a significant barrier to global poliomyelitis eradication. Following 18 years of polio-free status, an epidemic of circulating VDPV type 1 (cVDPV1) occurred in Papua New Guinea (PNG) in 2018. We describe the epidemiology of the 2018 cVDPV1 epidemic in PNG, and identify risk factors which may aid future policy and control efforts.Methods: Data pertaining to the 2018 PNG epidemic were extracted from EPIWATCH and supplemented with data from other sources, such as the World Health Organization (WHO), and published literature. Descriptive analyses were undertaken, and key risk factors identified.Results: 26 cases of cVDPV1 were confirmed throughout the duration of the epidemic (April to October 2018) in nine provinces. Of the 26 cases, 19 (73%) were males and 7 (27%) were females, and most of the cases (73%) occurred in children under the age of five. Population immunization coverage of three doses of oral polio vaccine (OPV3) was found to fluctuate between 60- 80% between 2000 and 2018. Nonpolio Acute Flaccid Paralysis (NPAFP) surveillance rates were also found to be suboptimal over this period.Discussion: A combination of low routine immunization coverage, lacking supplementary immunization activities, and ineffective surveillance systems, in the context of a struggling health system, culminated in this epidemic. To prevent future poliomyelitis epidemics in PNG, emphasis must be placed on supporting the health system to maintain high vaccination coverage, in conjunction with robust and effective surveillance systems.

Detection of vaccine-derived poliovirus type 2 amid the burden of infectious diseases in the UK: A cause for alarm.

The re-emergence of polio in the UK reminds us that the global threat of polio remains. Viruses know no bounds or borders. COVID-19, Monkeypox, and polio are evidence of this. Poliomyelitis was once the leading cause of death and paralysis in the UK and globally. With the introduction of vaccines during the 1950s–1960s, polio was eradicated from most developed countries, including the UK. The last case of wild polio was in 1984, and the UK was polio-free in 2003. The recent detection of vaccine-derived poliovirus type 2 in London sewage samples is alarming. Routine inoculations were adversely affected due to COVID-19, and UK's wastewater monitoring program was suspended due to economic restrictions. The UK faces several challenges with the burden of COVID-19, Monkeypox, and the return of polio could further burden the already pandemic-stricken healthcare system. To prevent further epidemics in the UK, wastewater sampling remains crucial in evaluating, searching, and eradicating the spread of poliovirus. Further epidemiological surveillance in adjacent areas to the Beckton plant is crucial to filling any gaps in understanding the outbreak's extent and guiding the initiation of appropriate and timely public health measures. The importance of vaccination in unvaccinated or incompletely vaccinated individuals cannot be overstated, especially in areas where vaccination rates are low. The risk of polio remains globally until its complete eradication from endemic countries. Until elimination, a global effort should be made to minimize the risk and the consequent spread of poliovirus by maintaining strong population immunity levels through high vaccination coverage.

Polio returns to the USA: An epidemiological alert

On July 21, 2022, the USA witnessed the first case of poliomyelitis after 3 decades of its eradication. Poliomyelitis is a crippling disease that results from infection with any one of the three related poliovirus types (referred to as types P1, P2, and P3), members of the enterovirus (picornavirus) family. The New York State Department of Health confirmed that a case of paralytic poliomyelitis was reported from a 20-year-old Hungarian traveller residing in Rockland County. The detected viral sequence has been found to have vaccine-derived poliovirus type 2 (VDPV2) suggesting an origin from the live attenuated oral polio vaccine (OPV). Since immunisation remains the only preventable measure, this article explores suggestions from the Centers for Disease Control and Prevention on reliable Inactivated (killed) polio vaccination in high-risk patients along with early case detection and treatment. In light of the above-mentioned findings, this research further details future recommendations like cessation of the OPV, encouragement of inactivated polio vaccine (IPV) in vaccination schedules, sensitive epidemiological surveillance system and appropriate training for healthcare providers. The affected countries have been further advised to have effective outbreak response strategy plans in place so that they can respond and stay prepared for such outbreaks in the future.

Rare recurrences of poliomyelitis in non-endemic countries after eradication: a call for global action

Following the confirmation on July 21, 2022, of a case of poliomyelitis related to circulating vaccine-derived poliovirus (cVDPV) type 2 in an unvaccinated adult from Rockland County, NY, USA,1 there has been a renewed global drive to strengthen surveillance for the detection of cases and increase vaccination coverage against polio. This is the first known case of polio with paralysis in nearly a decade in the USA, a country that no longer administers the oral polio vaccine, which suggests that the virus could have been imported.

Emergence of vaccine-derived poliovirus in high-income settings in the absence of oral polio vaccine use

On June 22, 2022, the UK Health Security Agency announced that vaccine-derived poliovirus type 2 (VDPV2) had been repeatedly detected in sewage in London, UK.1 Several weeks later, the New York State Department of Health reported a case of acute flaccid paralysis caused by VDPV2 in an unvaccinated individual; the first case of poliomyelitis in almost a decade in the USA.2 A similar virus has also been detected in sewage from Jerusalem, Israel.3

Emergence of vaccine-derived poliovirus type 2 after using monovalent type 2 oral poliovirus vaccine in an outbreak response, Philippines.

ObjectiveIn response to an outbreak of circulating vaccine-derived poliovirus (cVDPV) type 2 in the Philippines in 2019–2020, several rounds of supplementary immunization activities using the monovalent type 2 oral poliovirus vaccine (OPV) were conducted for the first time in the Western Pacific Region. After use of the monovalent vaccine, the emergence of vaccine-derived poliovirus unrelated to the outbreak virus was detected in healthy children and environmental samples. This report describes the detection of this poliovirus in the Philippines after use of the monovalent type 2 OPV for outbreak response.MethodsWe describe the emergence of vaccine-derived poliovirus unrelated to the outbreak detected after supplementary immunization activities using the monovalent type 2 OPV. This analysis included virus characterization, phylogenetic analyses and epidemiological investigations.ResultsThree environmental samples and samples from six healthy children tested positive for the emergent vaccine-derived poliovirus. All isolates differed from the Sabin type 2 reference strain by 6–13 nucleotide changes, and all were detected in the National Capital Region and Region 4, which had conducted supplementary immunization activities.DiscussionSince the 2016 removal of type 2 strains from the OPV, vaccine-derived poliovirus outbreaks have occurred in communities that are immunologically naive to poliovirus type 2 and in areas with recent use of monovalent OPV. To prevent the emergence and further spread of cVDPV type 2, several interventions could be implemented including optimizing outbreak responses by using the monovalent type 2 OPV, accelerating the availability of the novel type 2 OPV, strengthening routine immunization using inactivated polio vaccine and eventually replacing OPV with inactivated poliovirus vaccine for routine immunization.

The sensitivity of acute flaccid paralysis surveillance - the case of South Sudan: retrospective secondary analysis of AFP surveillance data 2014-2019.

IntroductionSouth Sudan has made quite impressive progress in interrupting wild poliovirus and maintaining a polio-free status since the last case was reported in 2009. South Sudan introduced different complementary strategies to enhance acute flaccid paralysis (AFP) surveillance. Hence, the objective of this study is to evaluate the sensitivity of the surveillance system using the WHO recommended surveillance standard and highlight the progress and challenges over the years.Methodswe conducted a retrospective, descriptive, quantitative study design and used the available secondary AFP surveillance database.Resultsthe overall non-polio AFP rate was 6.2/100,000 children under 15 years old in the study period. The stool adequacy was maintained well above the certification level of surveillance. The two main surveillance performance indicators were met at the national level throughout the study period. In contrast, only five out of ten states persistently attained and maintained the two main surveillance performance indicators throughout the study period, while in 2019 all states achieved except for Jonglei state. During the analysis period, no wild poliovirus was isolated except two circulating Vaccine Derived Poliovirus Type 2 (cVDPV2) cases in 2014 and one Immunodeficiency Vaccine Derived Poliovirus Type 2 (iVDPV2) case in 2015. However, on average, three cases were classified as polio compatible with each year of the study.ConclusionSouth Sudan met the two key surveillance performance indicators and had a sensitive AFP surveillance system during the period studied. We recommend intensifying surveillance activities in the former conflict-affected states and counties to maintain polio-free status.

Acute flaccid paralysis surveillance performance from 2011 to 2020 in Jonglei State, South Sudan: progress and challenges encountered.

IntroductionSouth Sudan reported the last indigenous wild poliovirus (WPV) in 2001 in Unity State, while the country was part of Sudan. In addition, the country reported an imported case of WPV in 2004-2005 and 2008-2009. The WPV circulation in the state was interrupted in 2009 and the last case was reported in Ayod county. The country continues to be at risk of importation of circulating vaccine-derived poliovirus type 2 (cVDPV2). In 2014 and 2020 the country experienced an outbreak of cVDPV2, in which Jonglei state was one of the affected states. Four out of 50 (8%) cVDPV2 cases in 2020 were reported from Jonglei State. The purpose of this study is to review surveillance performance indicators of Jonglei and compare them with the WHO surveillance performance standard and other country´s surveillance performances.Methodsretrospective secondary data analysis was conducted using the Jonglei state Acute Flaccid Paralysis (AFP) surveillance case-based database from 2011 to 2020. The reason for selecting Jonglei is because it is one of the poor performing states and is chronically hit by flood and internal conflicts. Data analyses were carried out using the Microsoft Excel (2016) program, where descriptive analysis frequencies, tables, and graphs were generated.Resultsthe study revealed that 346 AFP cases were reported in the counties of Jonglei state from 2011 through 2020. Out of 11 counties, 11 (100%) of them have reported suspected AFP cases. Children under five years accounted for 275 (79%) of all cases. The male gender accounted for 175 (51%) of all cases. A total of 249 (72%) had received three or more doses of Oral Polio Vaccine (OPV). Non-Polio Acute Flaccid Paralysis (NPAFP) rate varies from 1.2 in 2014 to 4.4 cases per 100,000 children under 15 years in 2018. The stool adequacy ranges from 58% in 2020 to 100% in 2011.Conclusionthe performance of Jonglei´s AFP surveillance system did not meet the WHO recommended target for both major AFP surveillance indicators (non-polio AFP rate and stool adequacy) during the study period.

Re-emergence of poliomyelitis in the Ukraine, caused by circulating vaccine-derived poliovirus type 2 (cVDPV2)

On October 2nd, 2021, a case of circulating vaccine-derived poliovirus type 2 (cVDPV2) was notified to the World Health Organisation from the Rivne Oblast of Ukraine. The index case was a seventeen-month-old unvaccinated girl who had an onset of acute flaccid paralysis (AFP) on September 1st, 2021. A second cVDPV2 case of an unvaccinated 2-year-old boy was reported from Transcarpathia Oblast on December 13th, 2021, who subsequently developed AFP on December 24th, 2021. A further 19 close contacts were identified with cVDPV2 that did not develop AFP that were all linked to the index case. Poliomyelitis outbreaks have occurred infrequently in the Ukraine since 2015, after being certified polio-free in 2002. The current outbreak has occurred against the backdrop of suboptimal vaccination coverage across the Ukraine since the previous outbreak saw a serious vaccine push across the country. However, the latest vaccine push in February 2022 has stalled due to the Russia-Ukraine war, leaving citizens displaced in shelters and border crossings, unable to access healthcare or routine immunisations.

Circulating vaccine derived polio virus type 1 outbreak, Saadah governorate, Yemen, 2020

BackgroundYemen has faced one of the worst humanitarian crises in the world since the start of the war in 2015. In 2020; 30 Vaccine Derived Polio Virus type 1 (VDPV1) isolates were detected in Saadah governorate. The aims are to characterize the outbreak and address the gaps predisposing the emergence and circulation of VDPV1 in Saadah governorate, Yemen.MethodA retrospective descriptive study of confirmed cases of VDPV1 between January and December 2020 was performed. Surveillance staff collected data from patient cases, contacts, as well as stool specimens that shipped to WHO accredited polio labs. Data of population immunity was also reviewed. The difference in days between the date of sample collection, shipment, and receiving lab result was used to calculate the average of delayed days for lab confirmation.ResultsFrom January to December 2020, a total of 114 cases of acute flaccid paralysis (AFP) were reported from 87% (13/15) districts, and cVDPV1 was confirmed among 26% (30) AFP cases. 75% (21) were < 5 years, 73% (20) had zero doses of Oral Polio Vaccine (OPV). The first confirmed case (3%) was from Saadah city, with paralysis onset at the end of January 2020 followed by 5 cases (17%) in March from another four districts, 8 cases (27%) in April, and 13 (43%) up to December 2020 were from the same five districts in addition to 3 (10%) form three new districts. The lab confirmation was received after an average of 126 days (71–196) from sample collection. The isolates differ from the Sabin 1 type by 17- 30 VP1 nucleotides (nt) and were linked to VDPV1 with 13 (nt) divergence that isolated in July 2020 from stool specimens collected before one year from contacts of an inadequate AFP case reported from Sahar district.ConclusionThe new emerging VDPV1 was retrospectively confirmed after one year of sample collection from Sahar district. Delayed lab confirmation, as well as the response and low immunization profile of children against polio, were the main predisposing factors for cVDPV1 outbreak. This outbreak highlights the need to maintain regular biweekly shipments to referral polio labs in the short-term, and the exploration of other options in the longer-term to enable the Yemen National Lab to fully process national samples itself.

Environmental Monitoring for Enteroviruses in Maputo, Mozambique-2018.

Due to the possibility of wild poliovirus importation from endemic regions and the high circulation of vaccine-derived poliovirus type 2 in the African region, Mozambique implemented a surveillance program to monitor the circulation of enteroviruses in the environment. From January to November 2018, a period that immediately preceded the cVDPV outbreak in Africa, 63 wastewater samples were collected from different areas in Maputo city. A total of 25 samples (39.7%) were positive based on cell culture isolation. Non-polio enteroviruses were found in 24 samples (24/25; 96%), whereas 1 Sabin-related poliovirus was isolated. Neither wild nor vaccine-derived poliovirus was detected. High circulation of EVB species was detected. Environmental surveillance in the One Health approach, if effectively applied as support to acute flaccid paralysis, can be a powerful aid to the public health system to monitor poliovirus besides non-polio enteroviruses in polio-free areas.

Diphtheria and tetanus seroepidemiology among children in Ukraine, 2017

BackgroundThe drastic decline of Ukraine’s immunization coverage since 2009 led to concerns about potential resurgence diphtheria and tetanus, along with other vaccine-preventable diseases. MethodsTo assess population immunity against diphtheria and tetanus, we tested specimens from the serosurvey conducted in 2017 among children born in 2006–2015, the birth cohorts targeted by the nationwide outbreak response immunization following a circulating vaccine-derived poliovirus type 1 outbreak in Zakarpattya province in 2015. We surveyed four regions of Ukraine, using cluster sampling in Zakarpattya, Sumy, and Odessa provinces and simple random sampling in Kyiv City. We tested serum specimens for IgG antibodies against diphtheria and tetanus, using microbead assays (MBA). We estimated seroprevalence and calculated 95% confidence intervals. We also obtained information on the immunization status of surveyed children. ResultsSeroprevalence of ≥0.1 IU/mL diphtheria antibodies was <80% in all survey sites (50.0%–79.2%). Seroprevalence of ≥0.1 IU/mL tetanus antibodies was ≥80% in Sumy, Kyiv City, and Odessa (80.2%–89.1%) and 61.6% in Zakarpattya. Across the sites, the proportion of children vaccinated age-appropriately with diphtheria-tetanus-containing vaccines (DTCV) was 28.5%–57.4% among children born in 2006–2010 and 34.1%–54.3% among children born in 2011–2015. The proportion of recipients of <3 DTCV doses increased from 7.1%–16.7% among children born in 2006–2010 to 19.8%–38.6% among children born in 2011–2015, as did the proportion of recipients of zero DTCV doses (2.6%–8.8% versus 8.0%–14.0%, respectively). ConclusionsProtection against diphtheria among children born in 2006–2015 was suboptimal (<80%), particularly in Zakarpattya. Protection against tetanus was adequate (≥80%) except in Zakarpattya. Diphtheria-tetanus immunization status was suboptimal across all sites. Catch-up vaccination of unvaccinated/under-vaccinated children and other efforts to increase immunization coverage would close these immunity gaps and prevent the resurgence of diphtheria and tetanus in Ukraine, particularly in Zakarpattya.

Curbing an outbreak of circulating vaccine derived poliovirus type 2 in Dollo Zone, Somali Region, Ethiopia: response to outbreak.

Introductionalthough the oral polio vaccine prevents virus transmission from person to person, it is crucial for poliovirus eradication. The continued use of live attenuated poliovirus poses an ongoing risk of circulating Vaccine Derived Poliovirus-2 (cVDPV2) outbreaks. This study assesses the response to the cVDPV2 outbreak in Dollo Zone, Somali Region, Ethiopia.Methodsafter examining and verifying the occurrence of the outbreak, a team was established and prepared by resource mobilization, advocacy, and social mobilization. The group endorsed a four-step vaccination strategy, first the rapid response within 14-days by vaccinating a monovalent oral poliovirus-2 (mOPV2) to all under 5-year children in the Zone. The team further enhanced Supplementary Immunization Activities (SIA) for all under-five children with repeated doses of vaccines. At the same time, the team initiated community-based surveillance of Acute Flaccid Paralysis (AFP).Resultsin the rapid-response immunization, an average of 91.4% of 0-11 months old and 90.2% of 12-59 months children were vaccinated. In SIA-1, the team vaccinated an average of 88% and 97%, and in SIA-2, 94.8% and 97.6% of children 0-11 months old and 12-59 months old, respectively. The active community-based surveillance of AFP revealed the existence of the disease in a sporadic form, of which two cases were found in Bokh district.Conclusionthe response to curb the outbreak of cVDPV2 has shown a flow of actions to combat the outbreak. Strengthening and formation of response teams at different levels, resource mobilization, advocacy, and social mobilization are all essential components in maximizing the response to the outbreak.

Intradermal administration of fractional doses of the inactivated poliovirus vaccine in a campaign: a pragmatic, open-label, non-inferiority trial in The Gambia

SummaryBackgroundA rapid increase in circulating vaccine-derived poliovirus type 2 outbreaks, and the need to reserve inactivated poliovirus vaccine (IPV) for routine immunisation, has increased the value of fractional dose IPV (fIPV) as a measure to prevent acute flaccid paralysis. However, the intradermal route of administration has been viewed as prohibitive to outbreak response campaigns. We aimed to establish the immunogenicity and safety of administering intradermal fIPV with a disposable syringe jet injector (DSJI) or an intradermal adaptor (IDA) compared with standard administration with a BCG needle and syringe (N&S).MethodsThis pragmatic, non-inferiority trial was undertaken in a campaign setting in communities in The Gambia. Children aged 4–59 months without contraindication to vaccination were eligible. Children were not individually randomly assigned; instead, the vaccination teams were randomly assigned (1:1:1) to one of three administration methods. Parents and the field team were not masked, but laboratory personnel were masked. Baseline demographic and anthropometric data were collected from the participants. Public health officers experienced at intradermal immunisation, and nurses without experience, had 2 h of training on each of the administration methods before the campaign. Participants were vaccinated using the administration method in use by the vaccination team in their community. Poliovirus serum neutralising antibodies (SNA) were measured in children aged 24–59 months before and 4 weeks after vaccination. Adverse events and data on injection quality were collected from all participants. The primary outcome was the type 2 immune response rate (seroconversion in seronegative [SNA titre <8] children plus a 4-fold titre rise in seropositive children). Adjusted differences in the immune response between the DSJI or IDA group versus the N&S group were calculated with 97·5% CIs. A margin of −10% was used to define the non-inferiority of DSJI or IDA compared to N&S. Immunogenicity analysis was done per protocol. The trial is registered with ClinicalTrials.govNCT02967783 and has been completed.FindingsBetween Oct 28 and Dec 29, 2016, 3189 children aged 4–59 months were recruited, of whom 3170 were eligible. Over 3 days, 2720 children were vaccinated (N&S, 917; IDA, 874; and DSJI, 929). Among 992 children aged 25–59 months with a baseline SNA available, 90·1% (95% CI 86·1–92·9; 281/312) of those vaccinated using the DSJI had an immune response to type 2 compared with 93·8% (90·6–95·8; 331/353) of those vaccinated with N&S and 96·6% (94·0–98·0; 316/327) of those vaccinated with IDA. All (53/53) type 2 seronegative children seroconverted. For polio type 2, non-inferiority was shown for both the IDA (adjusted difference 0·7% [97·5% CI −3·3 to 4·7], unadjusted difference 2·9% [–0·9 to 6·8]) and DSJI (adjusted difference −3·3% [–8·3 to 1·5], unadjusted difference −3·7% [–8·7 to 1·1]) compared with N&S. Non-inferiority was shown for type 1 and 3 for the IDA and DSJI. Neither injection quality nor the training and experience of the vaccinators had an effect on immune response. No safety concerns were reported.InterpretationIn a campaign, intradermal fIPV is safe and generates consistent immune responses that are not dependent on vaccinator experience or injection quality when administered using an N&S, DSJI, or IDA. Countries facing vaccine-derived poliovirus type 2 outbreaks should consider fIPV campaigns to boost population immunity and prevent cases of acute flaccid paralysis.FundingWorld Health Organization and the Medical Research Council.

Multiscale model for forecasting Sabin 2 vaccine virus household and community transmission.

Since the global withdrawal of Sabin 2 oral poliovirus vaccine (OPV) from routine immunization, the Global Polio Eradication Initiative (GPEI) has reported multiple circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreaks. Here, we generated an agent-based, mechanistic model designed to assess OPV-related vaccine virus transmission risk in populations with heterogeneous immunity, demography, and social mixing patterns. To showcase the utility of our model, we present a simulation of mOPV2-related Sabin 2 transmission in rural Matlab, Bangladesh based on stool samples collected from infants and their household contacts during an mOPV2 clinical trial. Sabin 2 transmission following the mOPV2 clinical trial was replicated by specifying multiple, heterogeneous contact rates based on household and community membership. Once calibrated, the model generated Matlab-specific insights regarding poliovirus transmission following an accidental point importation or mass vaccination event. We also show that assuming homogeneous contact rates (mass action), as is common of poliovirus forecast models, does not accurately represent the clinical trial and risks overestimating forecasted poliovirus outbreak probability. Our study identifies household and community structure as an important source of transmission heterogeneity when assessing OPV-related transmission risk and provides a calibratable framework for expanding these analyses to other populations.Trial Registration: ClinicalTrials.gov This trial is registered with clinicaltrials.gov, NCT02477046.

A Survey to Assess Serological Prevalence of Poliovirus Antibodies in Areas With High-Risk for Vaccine-Derived Poliovirus Transmission in Chad.

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

Enhancing acute flaccid paralysis surveillance system towards polio eradication: reverse cold chain monitoring in Nigeria, 2017 to 2019.

IntroductionHighly sensitive acute flaccid paralysis (AFP) surveillance is critical for detection of poliovirus circulation and documentation for polio-free certification. The reverse cold chain (RCC) is a system designed to maintain stool specimens in appropriate temperature for effective detection of poliovirus in the laboratory. We monitored the RCC of AFP surveillance in Nigeria to determine its effectiveness in maintaining viability of enterovirus.MethodsA descriptive cross-sectional study was conducted from November 2017 to December 2019. We included AFP cases from 151 Local Government Areas and monitored RCC of paired stool specimens from collection to arrival at laboratories. The national guideline recommends RCC temperature of +2 to +8°C and a non-polio enterovirus (NPENT) detection rate of ≥10%. We analyzed data with Epi Info 7, and presented results as frequencies and proportions, using Chi-square statistic to test for difference in enterovirus isolation.ResultsOf the 1,042 tracked paired stool specimens, 1,038(99.6%) arrived at the laboratory within 72 hours of collection of second specimen, 824(79.1%) were maintained within recommended temperature range, and 271(26%) yielded enteroviruses: 200(73.8%) NPENT, 66(24.4%) Sabin, 3(1.1%) vaccine derived poliovirus type 2 and 2(0.7%) mixture of Sabin and NPENT. The NPENT and Sabin rates were 19.2% and 6.7% respectively. Twenty-five percent of 824 specimens maintained within recommended temperature range, compared with 29.8% of 218 specimens with temperature excursion yielded enteroviruses (P=0.175).Conclusionthe RCC of AFP surveillance system in the study area was optimal and effective in maintaining the viability of enteroviruses. It was unlikely that poliovirus transmission was missed during the intervention.

Sensitivity of the acute flaccid paralysis surveillance system for poliovirus in South Africa, 2016-2019.

IntroductionGlobal poliovirus eradication is a public health emergency of international concern. The acute flaccid paralysis (AFP) surveillance programme in South Africa has been instrumental in eliminating polioviruses and keeping the country poliovirus free.Gap statementThe sensitivity of surveillance for polioviruses by every African country is of global interest in the effort to ensure global health security from poliovirus re-emergence.AimTo describe the epidemiology of polioviruses from AFP cases and environmental samples in South Africa and to report the performance of the AFP surveillance system for the years 2016–2019 against targets established by the World Health Organization (WHO).MethodsStool specimens from AFP or suspected AFP cases were received and tested as per WHO guidelines. Environmental samples were gathered from sites across the Gauteng province using the grab collection method. Concentration was effected by the two-phase polyethylene glycol method approved by the WHO. Suspected polioviruses were isolated in RD and/or L20B cell cultures through identification of typical cytopathic effects. The presence of polioviruses was confirmed by intratypic differentiation PCR. All polioviruses were sequenced using the Sanger method, and their VP1 gene analysed for mutations.ResultsData from 4597 samples (2385 cases) were analysed from the years 2016–2019. Two cases of immunodeficiency-associated vaccine-derived poliovirus (iVDPV) type 3 were detected in 2017 and 2018. A further 24 Sabin type 1 or type 3 polioviruses were detected for the 4 years. The national surveillance programme detected an average of 3.1 cases of AFP/100 000 individuals under 15 years old (2.8/100 000–3.5/100 000). The stool adequacy of the samples received was 53.0 % (47.0–55.0%), well below the WHO target of 80 % adequacy. More than 90 % of results were released from the laboratory within the turnaround time (96.6 %) and non-polio enteroviruses were detected in 11.6 % of all samples. Environmental surveillance detected non-polio enterovirus in 87.5 % of sewage samples and Sabin polioviruses in 12.5 % of samples.ConclusionThe AFP surveillance programme in South Africa is sensitive to detect polioviruses in South Africa and provided no evidence of wild poliovirus or VDPV circulation in the country.

Achieving High Poliovirus Antibody Seroprevalence in Areas at Risk of Vaccine-Derived Poliovirus Transmission-Niger Experience.

Background Outbreaks of vaccine-derived poliovirus type 2 (VDPV2) continue to expand across Africa. We conducted a serological survey of polio antibodies in high–polio risk areas of Niger to assess risk of poliovirus outbreaks.MethodsChildren between 1 and 5 years of age were enrolled from structures randomly selected using satellite imaging enumeration in Diffa Province, Niger, in July 2019. After obtaining informed consent, dried blood spot cards were collected. Neutralizing antibodies against 3 poliovirus serotypes were detected using microneutralization assay at the Centers for Disease Control and Prevention.ResultsWe obtained analyzable data from 309/322 (95.9%) enrolled children. Seroprevalence of polio antibodies was 290/309 (93.9%), 272/309 (88.0%), and 254/309 (82.2%) for serotypes 1, 2, and 3, respectively. For serotypes 1 and 2, the seroprevalence did not significantly change with age (P = .09 and P = .44, respectively); for serotype 3, it increased with age (from 65% in 1–2-year-olds to 91.1% in 4–5-year olds; P < .001). We did not identify any risk factors for type 2 seronegativity.Conclusions With type 2 seroprevalence close to 90%, the risk of emergence of new cVDPV2 outbreaks in Niger is low; however, the risk of cVDPV2 importations from neighboring countries leading to local transmission persists. Niger should maintain its outbreak response readiness capacity and further strengthen its routine immunization.