Last data update: Apr 29, 2024. (Total: 46658 publications since 2009)
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Poliovirus immunity among children aged 6-11 and 36-48 months in 14 polio high-risk provinces of Afghanistan: A health-facility-based study
Soofi SB , Martinez M , Farag NH , Hendley WS , Ehrhardt D , Ahmed I , Hussain I , Weldon W , Kassem AM . Vaccines (Basel) 2022 10 (10) Afghanistan is one of two countries where wild poliovirus (WPV) type 1 remains endemic. We conducted a facility-based cross-sectional survey of antipoliovirus antibodies in children in 14 provinces of Afghanistan. The provinces were selected based on programmatic priorities for polio eradication. Children aged 6-11 and 36-48 months attending outpatient clinics were enrolled in the study. We collected venous blood, isolated serum, and conducted neutralization assays to detect poliovirus neutralizing antibodies. A total of 2086 children from the 14 provinces were enrolled. Among the enrolled children, 44.3% were girls; the median age in the 6-11-month group was 9.4 months, and in the 36-48-month group, it was 41.8 months. The most common spoken language was Pashtu (70.8%). Eighty-two percent of children were fully immunized against all the diseases in the vaccination schedule of Afghanistan. In the children aged 6-11 months, seroprevalence to poliovirus type 1 (PV1) was 96.5% and seroprevalence to poliovirus type 3 (PV3) was 93%; in children aged 36-48 months, seroprevalence to PV1 was 99.5% and to PV3 was 98%. Antipoliovirus antibody prevalence for poliovirus type 2 (PV2) was 70.5% in the younger group compared with 90.9% in the older children. Children from Herat and Laghman provinces had almost 100% seroprevalence to PV1, and other provinces also had high prevalence, ranging from 92.0% to 99.0%. A similar finding was seen for antibodies against PV3, ranging from 88% to 100% by province. On the contrary, antibodies to PV2 were low, ranging from 53% for children in the Khost province to around 89% in Kunduz. There was a cluster of 18 seronegative children in the Nuristan province. Overall, the polio eradication program of Afghanistan has been successful in achieving high seroprevalence of poliovirus neutralizing antibodies in the parts of the country included in this study. |
Spatial analysis of genetic clusters and epidemiologic factors related to wild poliovirus type 1 persistence in Afghanistan and Pakistan.
Mendesid A , Whiteman A , Bullard K , Sharif S , Khurshidid A , Alam MM , Salman M , Fordid V , Blairid T , Burns CC , Ehrhardt D , Jorba J , Hsuid CH . PLoS Glob Public Health 2022 2 (6) e0000251 Following the certification of the World Health Organization Region of Africa as free of serotype 1 wild poliovirus (WPV1) in 2020, Afghanistan and Pakistan represent the last remaining WPV1 reservoirs. As efforts continue in these countries to progress to eradication, there is an opportunity for a deeper understanding of the spatiotemporal characteristics and epidemiological risk factors associated with continual WPV1 circulation in the region. Using poliovirus surveillance data from 2017-2019, we used pairwise comparisons of VP1 nucleotide sequences to illustrate the spatiotemporal WPV1 dispersal to identify key sources and destinations of potentially infected, highly mobile populations. We then predicted the odds of WPV1 detection at the district level using a generalized linear model with structural indicators of health, security, environment, and population demographics. We identified evidence of widespread population mobility based on WPV1 dispersal within and between the countries, and evidence indicating five districts in Afghanistan (Arghandab, Batikot, Bermel, Muhamandara and Nawzad) and four districts in Pakistan (Charsada, Dera Ismail Khan, Killa Abdullah and Khyber) act as cross-border WPV1 circulation reservoirs. We found that the probability of detecting WPV1 in a district increases with each armed conflict event (OR = 1.024, +- 0.008), level of food insecurity (OR = 1.531, +-0.179), and mean degrees Celsius during the months of greatest precipitation (OR = 1.079, +- 0.019). Our results highlight the multidisciplinary complexities contributing to the continued transmission of WPV1 in Afghanistan and Pakistan. We discuss the implications of our results, stressing the value of coordination during this final chapter of the wild polio virus eradication initiative. |
The immediate impact of the COVID-19 pandemic on polio immunization and surveillance activities.
Burkholder B , Wadood Z , Kassem AM , Ehrhardt D , Zomahoun D . Vaccine 2021 41 Suppl 1 A2-A11 In addition to affecting individual health the COVID-19 pandemic has disrupted efforts to deliver essential health services around the world. In this article we present an overview of the immediate programmatic and epidemiologic impact of the pandemic on polio eradication as well as the adaptive strategic and operational measures taken by the Global Polio Eradication Initiative (GPEI) from March through September 2020. Shortly after the World Health Organization (WHO) declared a global pandemic on 11 March 2020, the GPEI initially redirected the programme's assets to tackle COVID-19 and suspended house-to-house supplementary immunization activities (SIAs) while also striving to continue essential poliovirus surveillance functions. From March to May 2020, 28 countries suspended a total of 62 polio vaccine SIAs. In spite of efforts to continue poliovirus surveillance, global acute flaccid paralysis (AFP) cases reported from January-July 2020 declined by 34% compared with the same period in 2019 along with decreases in the mean number of environment samples collected per active site in the critical areas of the African and Eastern Mediterranean regions. The GPEI recommended countries should resume planning and implementation of SIAs starting in July 2020 and released guidelines to ensure these could be done safely for front line workers and communities. By the end of September 2020, a total of 14 countries had implemented circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreak response vaccination campaigns and Afghanistan and Pakistan restarted SIAs to stop ongoing wild poliovirus type 1 (WPV1) transmission. The longer-term impacts of disruptions to eradication efforts remain to be determined, especially in terms of the effect on poliovirus epidemiology. Adapting to the pandemic situation has imposed new considerations on program implementation and demonstrated not only GPEI's contribution to global health security, but also identified potential opportunities for coordinated approaches across immunization and health services. |
Stopping a polio outbreak in the midst of war: Lessons from Syria
Mbaeyi C , Moran T , Wadood Z , Ather F , Sykes E , Nikulin J , Al Safadi M , Stehling-Ariza T , Zomahoun L , Ismaili A , Abourshaid N , Asghar H , Korukluoglu G , Duizer E , Ehrhardt D , Burns CC , Sharaf M . Vaccine 2021 39 (28) 3717-3723 BACKGROUND: Outbreaks of circulating vaccine-derived polioviruses (cVDPVs) pose a threat to the eventual eradication of all polioviruses. In 2017, an outbreak of cVDPV type 2 (cVDPV2) occurred in the midst of a war in Syria. We describe vaccination-based risk factors for and the successful response to the outbreak. METHODS: We performed a descriptive analysis of cVDPV2 cases and key indicators of poliovirus surveillance and vaccination activities during 2016-2018. In the absence of reliable subnational coverage data, we used the caregiver-reported vaccination status of children with non-polio acute flaccid paralysis (AFP) as a proxy for vaccination coverage. We then estimated the relative odds of being unvaccinated against polio, comparing children in areas affected by the outbreak to children in other parts of Syria in order to establish the presence of poliovirus immunity gaps in outbreak affected areas. FINDINGS: A total of 74 cVDPV2 cases were reported, with paralysis onset ranging from 3 March to 21 September 2017. All but three cases were reported from Deir-ez-Zor governorate and 84% had received < 3 doses of oral poliovirus vaccine (OPV). After adjusting for age and sex, non-polio AFP case-patients aged 6-59 months in outbreak-affected areas had 2.5 (95% CI: 1.1-5.7) increased odds of being unvaccinated with OPV compared with non-polio AFP case-patients in the same age group in other parts of Syria. Three outbreak response rounds of monovalent OPV type 2 (mOPV2) vaccination were conducted, with governorate-level coverage mostly exceeding 80%. INTERPRETATION: Significant declines in both national and subnational polio vaccination coverage, precipitated by war and a humanitarian crisis, led to a cVDPV2 outbreak in Syria that was successfully contained following three rounds of mOPV2 vaccination. |
Progress toward poliomyelitis eradication - Pakistan, January 2019-September 2020
Hsu CH , Rehman MS , Bullard K , Jorba J , Kader M , Young H , Safdar M , Jafari HS , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2020 69 (46) 1748-1752 Pakistan and Afghanistan are the only countries where wild poliovirus type 1 (WPV1) is endemic (1,2). In 2019, Pakistan reported 147 WPV1 cases, approximately 12 times the number reported in 2018. As of September 15, 72 cases had been reported in 2020. Since 2019, WPV1 transmission has also spread from Pakistan's core poliovirus reservoirs (Karachi, Peshawar, and Quetta block) to southern districts of Khyber Pakhtunkhwa (KP), Punjab, and Sindh provinces. Further, an outbreak of circulating vaccine-derived poliovirus type 2 (cVDPV2), first detected in July 2019, has caused 22 paralytic cases in 2019 and 59 as of September 15, 2020, throughout the country. The coronavirus disease 2019 (COVID-19) pandemic has substantially reduced delivery of polio vaccines through essential immunization (formerly routine immunization) and prevented implementation of polio supplementary immunization activities (SIAs)* during March-July 2020. This report describes Pakistan's progress in polio eradication during January 2019-September 2020 and updates previous reports (1,3,4). The Pakistan polio program has reinitiated SIAs and will need large, intensive, high-quality campaigns with strategic use of available oral poliovirus vaccines (OPVs)(†) to control the surge and widespread transmission of WPV1 and cVDPV2. |
Progress Toward Poliomyelitis Eradication - Afghanistan, January 2019-July 2020.
Martinez M , Akbar IE , Wadood MZ , Shukla H , Jorba J , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2020 69 (40) 1464-1468 Wild poliovirus type 1 (WPV1) transmission is ongoing only in Afghanistan and Pakistan (1). Following a decline in case numbers during 2013-2016, the number of cases in Afghanistan has increased each year during 2017-2020. This report describes polio eradication activities and progress toward polio eradication in Afghanistan during January 2019-July 2020 and updates previous reports (2,3). Since April 2018, insurgent groups have imposed bans on house-to-house vaccination. In September 2019, vaccination campaigns in areas under insurgency control were restarted only at health facilities. In addition, during March-June 2020, all campaigns were paused because of the coronavirus disease 2019 (COVID-19) pandemic. The number of WPV1 cases reported in Afghanistan increased from 21 in 2018 to 29 in 2019. During January-July 2020, 41 WPV1 cases were reported as of August 29, 2020 (compared with 15 during January-July 2019); in addition, 69 cases of circulating vaccine-derived poliovirus type 2 (cVDPV2), and one case of ambiguous vaccine-derived poliovirus type 2 (aVDPV2) (isolates with no evidence of person-to-person transmission or from persons with no known immunodeficiency) were detected. Dialogue with insurgency leaders through nongovernmental and international organizations is ongoing in an effort to recommence house-to-house campaigns, which are essential to stopping WPV1 transmission in Afghanistan. To increase community demand for polio vaccination, additional community health needs should be addressed, and polio vaccination should be integrated with humanitarian services. |
Estimating population immunity to poliovirus in Lebanon: Results from a seroprevalence survey, 2016
Mansour Z , Said R , Wannemuehler K , Weldon W , Estephan J , Khachan J , Warrak R , Hendley W , Ehrhardt D , Farag NH . Vaccine 2020 38 (31) 4846-4852 INTRODUCTION: Circulation of poliovirus in neighboring countries and mass population movement places Lebanon at risk of polio and other vaccine-preventable disease outbreaks. Determining population immunity levels is essential for guiding program planning and implementation of targeted supplementary immunization activities (SIAs) in governorates and subpopulations with low seroprevalence. METHODS: A cross-sectional multi-stage cluster survey was conducted during February-December 2016 in all six governorates of Lebanon adapted from the World Health Organization (WHO) recommended Expanded Progamme on Immunization (EPI) methodology. Sera from selected children aged 12-59 months were tested for poliovirus neutralizing antibodies. RESULTS: Of 2,164 children recruited in this study, 1,893 provided sufficient quantity of serum samples for laboratory testing. Seroprevalence for all three poliovirus serotypes was greater than 90% in all six governorates. Poliovirus vaccine coverage with three or more doses, based on vaccination cards or parental recall, ranged between 54.1% for children aged 36-47 months in the North and 83.5% for children aged 48-59 months in Beirut. CONCLUSION: Immunity to polioviruses was high in Lebanon in 2016 following a series of supplementary immunization activities. It is essential to continue strategies that increase vaccination coverage in order to sustain the considerably high immunity levels and prevent reintroduction and transmission of poliovirus. Educating caregivers and training health care workers on the standardized usage of home-based vaccination records is needed to guarantee the accuracy of records on children's vaccination status. |
Using nonpolio enterovirus detection to assess the integrity of stool specimens collected from acute flaccid paralysis cases in Somalia during 2014-2017
Ben Hamida A , Mohamed Ali K , Mdodo R , Mohamed A , Mengistu K , Nzunza RM , Farag NH , Ehrhardt DT , Elfakki E , Mbaeyi C . Open Forum Infect Dis 2020 7 (5) ofaa135 Background: Despite insecurity challenges in Somalia, key indicators for acute flaccid paralysis (AFP) surveillance have met recommended targets. However, recent outbreaks of vaccine-derived polioviruses have raised concerns about possible gaps. We analyzed nonpolio enterovirus (NPEV) and Sabin poliovirus isolation rates to investigate whether comparing these rates can inform about the integrity of stool specimens from inaccessible areas and the likelihood of detecting circulating polioviruses. Methods: Using logistic regression, we analyzed case-based AFP surveillance data for 1348 cases with onset during 2014-2017. We assessed the adjusted impacts of variables including age, accessibility, and Sabin-like virus isolation on NPEV detection. Results: NPEVs were more likely to be isolated from AFP case patients reported from inaccessible areas than accessible areas (23% vs 15%; P = .01). In a multivariable model, inaccessibility and detection of Sabin-like virus were positively associated with NPEV detection (adjusted odds ratio [AOR], 1.75; 95% confidence interval [CI], 1.14-2.65; and AOR, 1.79; 95% CI, 1.07-2.90; respectively), while being aged >/=5 years was negatively associated (AOR, 0.42; 95% CI, 0.20-0.85). Conclusions: Rates of NPEV and Sabin poliovirus detection in inaccessible areas suggest that the integrity of fecal specimens tested for AFP surveillance in Somalia can generate useful AFP data, but uncertainties remain about surveillance system quality. |
Assessment of in-country capacity to maintain communicable disease surveillance and response services after polio eradication-Somalia
Hsu CH , Harvey B , Mohamed A , Elfakki E , Ehrhardt D , Farag NH . Vaccine 2019 38 (5) 1220-1224 One objective of the 2013-2018 Global Polio Eradication Initiative (GPEI) Strategic Plan was the transition of GPEI polio essential functions to other public health programs [1]. For many developing countries, in addition to polio essential functions, GPEI funding has been supporting integrated communicable disease surveillance and routine immunization programs. As GPEI progresses toward polio eradication, GPEI funding for some polio-free countries is being scaled back. The Somalia Polio Eradication Program, led by international organizations in collaboration with local authorities, is a critical source of immunizations for >2.5 million children. In addition, the polio program has been supporting a range of communicable disease surveillance, basic health services (e.g. routine immunizations) as well as emergency response activities (e.g. outbreak response). To assess current capacities in Somalia, interviews were conducted with representatives of relief organizations and ministries of health (MoHs) from Somaliland, Puntland, and South-Central political zones to elicit their opinions on their agency's capacity to assume public health activities currently supported by GPEI funds. Seventy percent of international and 62% of representatives of domestic relief agencies reported low capacity to conduct communicable disease surveillance without GPEI funds. Responses from MoH representatives for the three zones in Somalia ranged from "very weak" to "strong" regarding capacity to conduct both polio and non-polio related communicable disease surveillance and outbreak response activities. Zones programs are unprepared to provide communicable diseases services if GPEI funding were substantially reduced abruptly. Polio transition planning must strategically plan for shifting of GPEI staffing, operational assets and funding to support identified gaps in Somalia's public health infrastructure. |
Progress toward poliomyelitis eradication - Pakistan, January 2018-September 2019
Hsu CH , Kader M , Mahamud A , Bullard K , Jorba J , Agbor J , Safi MM , Jafari HS , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2019 68 (45) 1029-1033 Afghanistan and Pakistan are the only countries that continue to confirm ongoing wild poliovirus type 1 (WPV1) transmission (1). During January 2018-September 2019 the number of WPV1 cases in Pakistan increased, compared with the number during the previous 4 years. This report updates previous reports on Pakistan's polio eradication activities, progress, and challenges (2,3). In 2018, Pakistan reported 12 WPV1 cases, a 50% increase from eight cases in 2017, and a 31% increase in the proportion of WPV1-positive sites under environmental surveillance (i.e., sampling of sewage to detect poliovirus). As of November 7, 2019, 80 WPV1 cases had been reported, compared with eight cases by the same time in 2018. An intensive schedule of supplementary immunization activities (SIAs)* implemented by community health workers in the core reservoirs (i.e., Karachi, Peshawar, and Quetta) where WPV1 circulation has never been interrupted, and by mobile teams, has failed to interrupt WPV1 transmission in core reservoirs and prevent WPV1 resurgence in nonreservoir areas. Sewage samples have indicated wide WPV1 transmission in nonreservoir areas in other districts and provinces. Vaccine refusals, chronically missed children, community campaign fatigue, and poor vaccination management and implementation have exacerbated the situation. To overcome challenges to vaccinating children who are chronically missed in SIAs and to attain country and global polio eradication goals, substantial changes are needed in Pakistan's polio eradication program, including continuing cross-border coordination with Afghanistan, gaining community trust, conducting high-quality vaccination campaigns, improving oversight of field activities, and improving managerial processes to unify eradication efforts. |
Estimating population immunity to poliovirus in Jordan's high-risk areas
Farag NH , Wannemuehler K , Weldon W , Arbaji A , Belbaisi A , Khuri-Bulos N , Ehrhardt D , Surour MR , ElhajQasem NS , Al-Abdallat MM . Hum Vaccin Immunother 2019 16 (3) 548-553 A community-based serosurvey was conducted among children ages 6-59 to assess population immunity in Jordan's high-risk areas following the Middle East polio outbreak response. The survey was a two-stage cluster-quota sample with high risk areas as the primary sampling units. High-risk areas included border and hard-to-reach areas, and areas with a high proportion of refugees, mobile communities and/or low coverage during previous immunization campaigns. Population immunity to poliovirus was high overall. In high-risk areas, Type 1 seroprevalence = 98% (95% CI = 96, 99), Type 2= 98 (95% CI = 96, 99) and Type 3= 96 (95% CI = 94, 98). Seroprevalence was higher in the refugee camps: Type 1 seroprevalence = 99.6 (95% CI = 97.9, 100); Type 2: 99.6 (95% CI = 97.9, 99.9), and Type 3: 100 (95% CI = 100,100). The vigilance that the Jordan Ministry of Health has placed on locating and vaccinating high-risk populations has been successful in maintaining high population immunity and averting polio outbreaks despite the influx of refugees from Syria. |
Progress Toward Poliomyelitis Eradication - Afghanistan, January 2018-May 2019.
Martinez M , Shukla H , Nikulin J , Mbaeyi C , Jorba J , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2019 68 (33) 729-733 Since October 2016, Afghanistan and Pakistan have been the only countries with reported cases of wild poliovirus type 1 (WPV1) (1). In Afghanistan, although the number of cases had declined during 2013-2016, the polio eradication program experienced challenges during 2017-2019. This report describes polio eradication activities and progress in Afghanistan during January 2018-May 2019 and updates previous reports (2,3). During May-December 2018, insurgent groups (antigovernment elements) banned house-to-house vaccination in most southern and southeastern provinces, leaving approximately 1 million children inaccessible to oral poliovirus vaccine (OPV) administration. During January-April 2019, vaccination targeting children at designated community sites (site-to-site vaccination) was permitted; however, at the end of April 2019, vaccination campaigns were banned nationally. During 2018, a total of 21 WPV1 cases were reported in Afghanistan, compared with 14 during 2017. During January-May 2019, 10 WPV1 cases were reported (as of May 31), compared with eight during January-May 2018. Sewage sample-testing takes place at 20 sites in the highest-risk areas for poliovirus circulation; 17 have detected WPV1 since January 2017, primarily in the southern and eastern provinces. Continued discussion with antigovernment elements to resume house-to-house campaigns is important to achieving polio eradication in Afghanistan. To increase community support for vaccination, collaboration among humanitarian service agencies to address other urgent health and basic needs is critical. |
Update on Vaccine-Derived Poliovirus Outbreaks - Democratic Republic of the Congo and Horn of Africa, 2017-2018.
Mbaeyi C , Alleman MM , Ehrhardt D , Wiesen E , Burns CC , Liu H , Ewetola R , Seakamela L , Mdodo R , Ndoutabe M , Wenye PK , Riziki Y , Borus P , Kamugisha C , Wassilak SGF . MMWR Morb Mortal Wkly Rep 2019 68 (9) 225-230 Widespread use of live attenuated (Sabin) oral poliovirus vaccine (OPV) has resulted in marked progress toward global poliomyelitis eradication (1). However, in underimmunized populations, extensive person-to-person transmission of Sabin poliovirus can result in genetic reversion to neurovirulence and paralytic vaccine-derived poliovirus (VDPV) disease (1). This report updates (as of February 26, 2019) previous reports on circulating VDPV type 2 (cVDPV2) outbreaks during 2017-2018 in the Democratic Republic of the Congo (DRC) and in Somalia, which experienced a concurrent cVDPV type 3 (cVDPV3) outbreak* (2,3). In DRC, 42 cases have been reported in four cVDPV2 outbreaks; paralysis onset in the most recent case was October 7, 2018 (2). Challenges to interrupting transmission have included delays in outbreak-response supplementary immunization activities (SIAs) and difficulty reaching children in all areas. In Somalia, cVDPV2 and cVDPV3 were detected in sewage before the detection of paralytic cases (3). Twelve type 2 and type 3 cVDPV cases have been confirmed; the most recent paralysis onset dates were September 2 (cVDPV2) and September 7, 2018 (cVDPV3). The primary challenge to interrupting transmission is the residence of >300,000 children in areas that are inaccessible for vaccination activities. For both countries, longer periods of surveillance are needed before interruption of cVDPV transmission can be inferred. |
Progress toward poliomyelitis eradication - Pakistan, January 2017-September 2018
Hsu C , Mahamud A , Safdar M , Nikulin J , Jorba J , Bullard K , Agbor J , Kader M , Sharif S , Ahmed J , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2018 67 (44) 1242-1245 Among the three wild poliovirus (WPV) serotypes, only WPV type 1 (WPV1) has been reported in polio cases or detected from environmental surveillance globally since 2012. Pakistan remains one of only three countries worldwide (the others are Afghanistan and Nigeria) that has never had interrupted WPV1 transmission. This report documents Pakistan's activities and progress toward polio eradication during January 2017-September 2018 and updates previous reports (1,2). In 2017, Pakistan reported eight WPV1 cases, a 60% decrease from 20 cases in 2016. As of September 18, 2018, four cases had been reported, compared with five cases at that time in 2017. Nonetheless, in 2018, WPV1 continues to be isolated regularly from environmental surveillance sites, primarily in the core reservoir areas of Karachi, Quetta, and Peshawar, signifying persistent transmission. Strategies to increase childhood immunity have included an intense schedule of supplemental immunization activities (SIAs), expanding and refining deployment of community-based vaccination implemented by community health workers recruited from the local community in reservoir areas, and strategic placement of permanent transit points where vaccination is provided to mobile populations. Interruption of WPV1 transmission will require further programmatic improvements throughout the country with a focus on specific underperforming subdistricts in reservoir areas. |
Notes from the field: Widespread transmission of circulating vaccine-derived poliovirus identified by environmental surveillance and immunization response - Horn of Africa, 2017-2018
Eboh VA , Makam JK , Chitale RA , Mbaeyi C , Jorba J , Ehrhardt D , Durry E , Gardner T , Mohamed K , Kamugisha C , Borus P , Elsayed EA . MMWR Morb Mortal Wkly Rep 2018 67 (28) 787-789 After the declaration of eradication of wild poliovirus type 2 in 2015, all countries using oral poliovirus vaccine (OPV) switched from using trivalent OPV (tOPV) (containing vaccine virus types 1, 2, and 3) to bivalent OPV (bOPV) (containing types 1 and 3) in April 2016 (1). Vaccine-derived polioviruses (VDPVs), strains that have diverged from the live vaccine virus during prolonged circulation, can emerge rarely in areas with inadequate OPV coverage and can cause outbreaks of paralysis. Before the global switch from tOPV to bOPV, many circulating VDPV (cVDPV) outbreaks identified globally were caused by type 2 cVDPV (cVDPV2). After the switch, two large cVDPV2 outbreaks occurred in 2017 in the Democratic Republic of the Congo (continuing in 2018) and Syria (2,3). |
Feasibility of jet injector use during inactivated poliovirus vaccine house-to-house vaccination campaigns
Farag NH , Mansour Z , Torossian L , Said R , Snider CJ , Ehrhardt D . Vaccine 2018 36 4935-4938 BACKGROUND: To attain high coverage during polio vaccination campaigns, an outreach house-to-house strategy is used to administer oral poliovirus vaccine. Administering an injectable vaccine house-to-house requires a skilled work force and increases risks of needle stick injuries. Needle-free injection devices provide a safer alternative to needles and syringes for administering injectable vaccines. We evaluated the feasibility and acceptability of a needle-free injection device to administer injectable poliovirus vaccine during a house-to-house vaccination outreach activity. METHODS: Vaccination teams administered injectable poliovirus vaccine using the Pharmajet(R) needle-free intramuscular jet injector to children ages 6-59months in 766 homes. Data on the feasibility of using the jet injector in an outreach campaign setting and the acceptability of the jet injector by caregivers and vaccinators were collected. RESULTS: A total of 993 injections were administered. Vaccinators faced challenges during device preparation in 16% (n=158) of injections; challenges were related to problems loading the injector and not having a flat surface to use for setup of the injector. Among 32 vaccinators interviewed after the vaccination campaign, the main reported advantage of the device was absence of sharps disposal (91%) while the main reported disadvantage was unacceptability by parents (90%) which was related to the vaccine, not the device. CONCLUSIONS: The needle-free jet injector was feasible for use in house-to-house campaigns. Acceptability by vaccinators was low as 81% stated that the jet injector was not easier to use than needle and syringe. Parental refusal related to frequent polio vaccination campaigns was the biggest challenge. In addition, novelty of the device posed a challenge to teams as they needed to reassure parents about safety of the device. To take full advantage of the ability to take injectable vaccines door-to-door during vaccination campaigns using a needle-free jet injector device, tailored social mobilization efforts are needed ahead of campaigns. |
Strategic Response to an Outbreak of Circulating Vaccine-Derived Poliovirus Type 2 - Syria, 2017-2018.
Mbaeyi C , Wadood ZM , Moran T , Ather F , Stehling-Ariza T , Nikulin J , Al Safadi M , Iber J , Zomahoun L , Abourshaid N , Pang H , Collins N , Asghar H , Butt OUI , Burns CC , Ehrhardt D , Sharaf M . MMWR Morb Mortal Wkly Rep 2018 67 (24) 690-694 Since the 1988 inception of the Global Polio Eradication Initiative (GPEI), progress toward interruption of wild poliovirus (WPV) transmission has occurred mostly through extensive use of oral poliovirus vaccine (OPV) in mass vaccination campaigns and through routine immunization services (1,2). However, because OPV contains live, attenuated virus, it carries the rare risk for reversion to neurovirulence. In areas with very low OPV coverage, prolonged transmission of vaccine-associated viruses can lead to the emergence of vaccine-derived polioviruses (VDPVs), which can cause outbreaks of paralytic poliomyelitis. Although WPV type 2 has not been detected since 1999, and was declared eradicated in 2015,* most VDPV outbreaks have been attributable to VDPV serotype 2 (VDPV2) (3,4). After the synchronized global switch from trivalent OPV (tOPV) (containing vaccine virus types 1, 2, and 3) to bivalent OPV (bOPV) (types 1 and 3) in April 2016 (5), GPEI regards any VDPV2 emergence as a public health emergency (6,7). During May-June 2017, VDPV2 was isolated from stool specimens from two children with acute flaccid paralysis (AFP) in Deir-ez-Zor governorate, Syria. The first isolate differed from Sabin vaccine virus by 22 nucleotides in the VP1 coding region (903 nucleotides). Genetic sequence analysis linked the two cases, confirming an outbreak of circulating VDPV2 (cVDPV2). Poliovirus surveillance activities were intensified, and three rounds of vaccination campaigns, aimed at children aged <5 years, were conducted using monovalent OPV type 2 (mOPV2). During the outbreak, 74 cVDPV2 cases were identified; the most recent occurred in September 2017. Evidence indicates that enhanced surveillance measures coupled with vaccination activities using mOPV2 have interrupted cVDPV2 transmission in Syria. |
Strengthening acute flaccid paralysis surveillance through the village polio volunteers program in Somalia
Mbaeyi C , Mohamed A , Owino BO , Mengistu KF , Ehrhardt D , Elsayed EA . Clin Infect Dis 2018 67 (6) 941-946 Background: Surveillance for cases of acute flaccid paralysis (AFP) is a key strategy adopted for the eradication of polio. Detection of poliovirus circulation is often predicated on the ability to identify AFP cases and test their stool specimens for poliovirus infection in a timely manner. The Village Polio Volunteers (VPV) program was established in 2013 in a bid to strengthen polio eradication activities in Somalia, including AFP surveillance, given the country's vulnerability to polio outbreaks. Methods: To assess the impact of the VPV program on AFP surveillance, we determined case counts, case-reporting sources, and non-polio AFP rates in the years before and after program introduction, i.e., 2011-2016. We also compared the stool adequacy and timeliness of cases reported by VPVs to those reported by other sources. Results: In the years following program introduction, VPVs accounted for a high proportion of AFP cases reported in Somalia. AFP case counts rose from 148 cases in 2012, the year before program introduction, to 279 cases in 2015, during which VPVs accounted for 40% of reported cases. Further, the non-polio AFP rate improved from 2.8 cases in 2012 to 4.8 cases per 100,000 persons <15 years by 2015. Stool adequacy rates have been consistently high and AFP cases have been detected in a timelier manner since the program was introduced. Conclusions: Given the impact of the VPV program on improving AFP surveillance indicators in Somalia, similar community-based programs could play a crucial role in enhancing surveillance activities in countries with limited healthcare infrastructure. |
Using predictive evaluation to design, evaluate, and improve training for polio volunteers
Traicoff DA , Basarab D , Ehrhardt DT , Brown S , Celaya M , Jarvis D , Howze EH . Pedagogy Health Promot 2018 4 (1) 35-42 Background: Predictive Evaluation (PE) uses a four-step process to predict results then designs and evaluates a training intervention accordingly. In 2012, the Sustainable Management Development Program (SMDP) at the Centers for Disease Control and Prevention used PE to train Stop Transmission of Polio (STOP) program volunteers. Methods: Stakeholders defined specific beliefs and practices that volunteers should demonstrate. These predictions and adult learning practices were used to design a curriculum to train four cohorts. At the end of each workshop, volunteers completed a beliefs survey and wrote goals for intended actions. The goals were analyzed for acceptability based on four PE criteria. The percentage of acceptable goals and the beliefs survey results were used to define the quality of the workshop. A postassignment adoption evaluation was conducted for two cohorts, using an online survey and telephone or in-person structured interviews. The results were compared with the end of workshop findings. Results: The percentage of acceptable goals across the four cohorts ranged from 49% to 85%. In the adoption evaluation of two cohorts, 88% and 94% of respondents reported achieving or making significant progress toward their goal. A comparison of beliefs survey responses across the four cohorts indicated consistencies in beliefs that aligned with stakeholders' predictions. Conclusions: Goal statements that participants write at the end of a workshop provide data to evaluate training quality. Beliefs surveys surface attitudes that could help or hinder workplace performance. The PE approach provides an innovative framework for health worker training and evaluation that emphasizes performance. |
Modeling poliovirus transmission in Pakistan and Afghanistan to inform vaccination strategies in undervaccinated subpopulations
Duintjer Tebbens RJ , Pallansch MA , Cochi SL , Ehrhardt DT , Farag NH , Hadler SC , Hampton LM , Martinez M , Wassilak SGF , Thompson KM . Risk Anal 2018 38 (8) 1701-1717 Due to security, access, and programmatic challenges in areas of Pakistan and Afghanistan, both countries continue to sustain indigenous wild poliovirus (WPV) transmission and threaten the success of global polio eradication and oral poliovirus vaccine (OPV) cessation. We fitted an existing differential-equation-based poliovirus transmission and OPV evolution model to Pakistan and Afghanistan using four subpopulations to characterize the well-vaccinated and undervaccinated subpopulations in each country. We explored retrospective and prospective scenarios for using inactivated poliovirus vaccine (IPV) in routine immunization or supplemental immunization activities (SIAs). The undervaccinated subpopulations sustain the circulation of serotype 1 WPV and serotype 2 circulating vaccine-derived poliovirus. We find a moderate impact of past IPV use on polio incidence and population immunity to transmission mainly due to (1) the boosting effect of IPV for individuals with preexisting immunity from a live poliovirus infection and (2) the effect of IPV-only on oropharyngeal transmission for individuals without preexisting immunity from a live poliovirus infection. Future IPV use may similarly yield moderate benefits, particularly if access to undervaccinated subpopulations dramatically improves. However, OPV provides a much greater impact on transmission and the incremental benefit of IPV in addition to OPV remains limited. This study suggests that despite the moderate effect of using IPV in SIAs, using OPV in SIAs remains the most effective means to stop transmission, while limited IPV resources should prioritize IPV use in routine immunization. |
Fractional-dose inactivated poliovirus vaccine campaign - Sindh Province, Pakistan, 2016
Pervaiz A , Mbaeyi C , Baig MA , Burman A , Ahmed JA , Akter S , Jatoi FA , Mahamud A , Asghar RJ , Azam N , Shah MN , Laghari MA , Soomro K , Wadood MZ , Ehrhardt D , Safdar RM , Farag N . MMWR Morb Mortal Wkly Rep 2017 66 (47) 1295-1299 Following the declaration of eradication of wild poliovirus (WPV) type 2 in September 2015, trivalent oral poliovirus vaccine (tOPV) was withdrawn globally to reduce the risk for type 2 vaccine-derived poliovirus (VDPV2) transmission; all countries implemented a synchronized switch to bivalent OPV (type 1 and 3) in April 2016 (1,2). Any isolation of VDPV2 after the switch is to be treated as a potential public health emergency and might indicate the need for supplementary immunization activities (3,4). On August 9, 2016, VDPV2 was isolated from a sewage sample taken from an environmental surveillance site in Hyderabad, Sindh province, Pakistan. Possible vaccination activities in response to VDPV2 isolation include the use of injectable inactivated polio vaccine (IPV), which poses no risk for vaccine-derived poliovirus transmission. Fractional-dose, intradermal IPV (fIPV), one fifth of the standard intramuscular dose, has been developed to more efficiently manage limited IPV supplies. fIPV has been shown in some studies to be noninferior to full-dose IPV (5,6) and was used successfully in response to a similar detection of a single VDPV2 isolate from sewage in India (7). Injectable fIPV was used for response activities in Hyderabad and three neighboring districts. This report describes the findings of an assessment of preparatory activities and subsequent implementation of the fIPV campaign. Despite achieving high coverage (>80%), several operational challenges were noted. The lessons learned from this campaign could help to guide the planning and implementation of future fIPV vaccination activities. |
Progress toward poliomyelitis eradication - Pakistan, January 2016-September 2017
Elhamidi Y , Mahamud A , Safdar M , Al Tamimi W , Jorba J , Mbaeyi C , Hsu CH , Wadood Z , Sharif S , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2017 66 (46) 1276-1280 In 1988, the World Health Assembly launched the Global Polio Eradication Initiative. Among the three wild poliovirus serotypes, only wild poliovirus (WPV) type 1 (WPV1) has been detected since 2012. Since 2014, Pakistan, Afghanistan, and Nigeria remain the only countries with continuing endemic WPV1 transmission. This report describes activities conducted and progress made toward the eradication of poliovirus in Pakistan during January 2016-July 2017 and provides an update to previous reports (1,2). In 2016, Pakistan reported 20 WPV1 cases, a 63% decrease compared with 54 cases in 2015 (3). As of September 25, 2017, five WPV1 cases have been reported in 2017, representing a 69% decline compared with 16 cases reported during the same period in 2016 (Figure 1). During January-September 2017, WPV1 was detected in 72 of 468 (15%) environmental samples collected, compared with 36 of 348 (9%) samples collected during the same period in 2016. WPV1 was detected in environmental samples in areas where no polio cases are being reported, which indicates that WPV1 transmission is continuing in some high-risk areas. Interruption of WPV transmission in Pakistan requires maintaining focus on reaching missed children (particularly among mobile populations), continuing community-based vaccination, implementing the 2017-2018 National Emergency Action Plan (4), and improving routine immunization services. |
Progress toward poliomyelitis eradication - Afghanistan, January 2016-June 2017
Martinez M , Shukla H , Nikulin J , Wadood MZ , Hadler S , Mbaeyi C , Tangermann R , Jorba J , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2017 66 (32) 854-858 Afghanistan, Pakistan, and Nigeria remain the only countries where the transmission of endemic wild poliovirus type 1 (WPV1) continues (1). This report describes polio eradication activities, progress, and challenges in Afghanistan during January 2016-June 2017 and updates previous reports (2,3). Thirteen WPV1 cases were confirmed in Afghanistan in 2016, a decrease of seven from the 20 cases reported in 2015. From January to June 2017, five WPV1 cases were reported, compared with six during the same period in 2016. The number of affected districts declined from 23 (including WPV1-positive acute flaccid paralysis [AFP] cases and positive environmental sewage samples) in 2015 to six in 2016. To achieve WPV1 eradication, it is important that Afghanistan's polio program continue to collaborate with that of neighboring Pakistan to track and vaccinate groups of high-risk mobile populations and strengthen efforts to reach children in security-compromised areas. |
Routine immunization service delivery through the basic package of health services program in Afghanistan: Gaps, challenges, and opportunities
Mbaeyi C , Kamawal NS , Porter KA , Azizi AK , Sadaat I , Hadler S , Ehrhardt D . J Infect Dis 2017 216 S273-S279 Background. The Basic Package of Health Services (BPHS) program has increased access to immunization services for children living in rural Afghanistan. However, multiple surveys have indicated persistent immunization coverage gaps. Hence, to identify gaps in implementation, an assessment of the BPHS program was undertaken, with specific focus on the routine immunization (RI) component. Methods. A cross-sectional survey was conducted in 2014 on a representative sample drawn from a sampling frame of 1858 BPHS health facilities. Basic descriptive analysis was performed, capturing general characteristics of survey respondents and assessing specific RI components, and ++ 2 tests were used to evaluate possible differences in service delivery by type of health facility. Results. Of 447 survey respondents, 27% were health subcenters (HSCs), 30% were basic health centers, 32% were comprehensive health centers, and 12% were district hospitals. Eighty-seven percent of all respondents offered RI services, though only 61% of HSCs did so. Compared with other facility types, HSCs were less likely to have adequate stock of vaccines, essential cold-chain equipment, or proper documentation of vaccination activities. Conclusions. There is an urgent need to address manpower and infrastructural deficits in RI service delivery through the BPHS program, especially at the HSC level. |
Response to a large polio outbreak in a setting of conflict - Middle East, 2013-2015
Mbaeyi C , Ryan MJ , Smith P , Mahamud A , Farag N , Haithami S , Sharaf M , Jorba JC , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2017 66 (8) 227-231 As the world advances toward the eradication of polio, outbreaks of wild poliovirus (WPV) in polio-free regions pose a substantial risk to the timeline for global eradication. Countries and regions experiencing active conflict, chronic insecurity, and large-scale displacement of persons are particularly vulnerable to outbreaks because of the disruption of health care and immunization services. A polio outbreak occurred in the Middle East, beginning in Syria in 2013 with subsequent spread to Iraq. The outbreak occurred 2 years after the onset of the Syrian civil war, resulted in 38 cases, and was the first time WPV was detected in Syria in approximately a decade. The national governments of eight countries designated the outbreak a public health emergency and collaborated with partners in the Global Polio Eradication Initiative (GPEI) to develop a multiphase outbreak response plan focused on improving the quality of acute flaccid paralysis (AFP) surveillance and administering polio vaccines to >27 million children during multiple rounds of supplementary immunization activities (SIAs). Successful implementation of the response plan led to containment and interruption of the outbreak within 6 months of its identification. The concerted approach adopted in response to this outbreak could serve as a model for responding to polio outbreaks in settings of conflict and political instability. |
Progress toward poliomyelitis eradication - Pakistan, January 2015-September 2016
Hsu CH , Mahamud A , Safdar RM , Ahmed J , Jorba J , Sharif S , Farag N , Martinez M , Tangermann RH , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2016 65 (46) 1295-1299 Pakistan, Afghanistan, and Nigeria remain the only countries where endemic wild poliovirus type 1 (WPV1) transmission continues. This report describes the activities, challenges, and progress toward polio eradication in Pakistan during January 2015-September 2016 and updates previous reports. In 2015, a total of 54 WPV1 cases were reported in Pakistan, an 82% decrease from 2014. In 2016, 15 WPV1 cases had been reported as of November 1, representing a 61% decrease compared with the 38 cases reported during the same period in 2015. Among the 15 WPV1 cases reported in 2016, children aged <36 months accounted for 13 cases; four of those children had received only a single dose of oral poliovirus vaccine (OPV). Seven of the 15 WPV1 cases occurred in the province of Khyber Pakhtunkhwa (KP), five in Sindh, two in the Federally Administered Tribal Areas (FATA), and one in Balochistan. During January-September 2016, WPV1 was detected in 9% (36 of 384) of environmental samples collected, compared with 19% (69 of 354) of samples collected during the same period in 2015. Rigorous implementation of the 2015-2016 National Emergency Action Plan (NEAP), coordinated by the National Emergency Operations Center (EOC), has resulted in a substantial decrease in overall WPV1 circulation compared with the previous year. However, detection of WPV1 cases in high-risk areas and the detection of WPV1 in environmental samples from geographic areas where no polio cases are identified highlight the need to continue to improve the quality of supplemental immunization activities (SIAs), immunization campaigns focused on vaccinating children with OPV outside of routine immunization services, and surveillance for acute flaccid paralysis (AFP). Continuation and refinement of successful program strategies, as outlined in the new 2016-2017 NEAP, with particular focus on identifying children missed by vaccination, community-based vaccination, and rapid response to virus identification are needed to stop WPV transmission. |
Progress toward poliomyelitis eradication - Afghanistan, January 2015-August 2016
Mbaeyi C , Shukla H , Smith P , Tangermann RH , Martinez M , Jorba JC , Hadler S , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2016 65 (43) 1195-1199 Only 74 cases of wild poliovirus (WPV) were reported globally in 2015, the lowest number of cases ever reported worldwide (1,2). All of the reported cases were WPV type 1 (WPV1), the only known WPV type still circulating; WPV type 2 has been eradicated, and WPV type 3 has not been detected since November 2012 (1). In 2015 in Afghanistan, WPV detection also declined from 2014, and trends observed in 2016 suggest that circulation of the virus is limited to a few localized areas. Despite the progress, there are concerns about the ability of the country's Polio Eradication Initiative (PEI) to meet the goal of interrupting endemic WPV transmission by the end of 2016 (3). The deteriorating security situation in the Eastern and Northeastern regions of the country considerably limits the ability to reach and vaccinate children in these regions. Furthermore, because of frequent population movements to and from Pakistan, cross-border transmission of WPV1 continues (4). Although the national PEI has taken steps to improve the quality of supplementary immunization activities (SIAs),* significant numbers of children living in accessible areas are still being missed during SIAs, and routine immunization services remain suboptimal in many parts of the country. This report describes polio eradication activities and progress in Afghanistan during January 2015August 2016 and updates previous reports (5,6). During 2015, a total of 20 WPV1 cases were reported in Afghanistan, compared with 28 cases in 2014; eight cases were reported during JanuaryAugust 2016, compared with nine cases reported during the same period in 2015. To achieve interruption of poliovirus transmission in Afghanistan, it is important that the 2016-2017 National Emergency Action Plandagger for polio eradication be systematically implemented, including 1) improving the quality of SIAs and routine immunization services, 2) ensuring ongoing dialogue between PEI leaders and local authorities, 3) adopting innovative strategies for reaching children in security-compromised and inaccessible areas, and 4) strengthening cross-border coordination of polio vaccination and surveillance activities with Pakistan. |
Contribution of contact sampling in increasing sensitivity of poliovirus detection during a polio outbreak - Somalia, 2013
Moturi E , Mahmud A , Kamadjeu R , Mbaeyi C , Farag N , Mulugeta A , Gary H Jr , Ehrhardt D . Open Forum Infect Dis 2016 3 (2) ofw111 Background. In May 2013, a wild poliovirus type 1 (WPV1) outbreak reported in Somalia provided an opportunity to examine the contribution of testing contacts to WPV detection. Methods. We reviewed acute flaccid paralysis (AFP) case-patients and linked contacts reported in the Somalia Surveillance Database from May 9 to December 31, 2013. We restricted our analysis to AFP case-patients that had ≥3 contacts and calculated the contribution of each contact to case detection. Results. Among 546 AFP cases identified, 328 AFP cases had ≥3 contacts. Among the 328 AFP cases with ≥3 contacts, 93 WPV1 cases were detected: 58 cases (62%; 95% confidence interval [CI], 52%-72%) were detected through testing stool specimens from AFP case-patients; and 35 cases (38%; 95% CI, 28%-48%) were detected through testing stool specimens from contacts, including 19 cases (20%; 95% CI, 14%-30%) from the first contact, 11 cases (12%; 95% CI, 7%-20%) from the second contact, and 5 cases (5%; 95% CI, 2%-12%) from the third contact. Among the 103 AFP cases with ≥4 contacts, 3 (6%; 95% CI, 2%-16%) of 52 WPV1 cases were detected by testing the fourth contact. No additional WPV1 cases were detected by testing >4 contacts. Conclusions. Stool specimens from 3 to 4 contacts of persons with AFP during polio outbreaks are needed to maximize detection of WPV cases. |
Progress toward poliomyelitis eradication - Pakistan, January 2014-September 2015
Farag NH , Wadood MZ , Safdar RM , Ahmed N , Hamdi S , Tangermann RH , Ehrhardt D . MMWR Morb Mortal Wkly Rep 2015 64 (45) 1271-5 Since Nigeria reported its last case of wild poliovirus type 1 (WPV1) in July 2014, Pakistan and Afghanistan remain the only two countries where WPV transmission has never been interrupted (1). This report describes actions taken and progress achieved toward polio eradication in Pakistan during January 2014-September 2015 and updates previous reports (2,3). A total of 38 WPV1 cases were reported in Pakistan during January-September 2015,* compared with 243 during the same period in 2014 (an 84% decline). Among WPV1 cases reported in 2015, 32 (84%) occurred in children aged <36 months, nine (32%) of whom had never received oral poliovirus vaccine (OPV). Twenty-six (68%) of the 38 reported cases occurred in the Federally Administered Tribal Areas (FATA) and Khyber Pakhtunkhwa (KPK) Province. During January-September 2015, WPV1 was detected in 20% (64 of 325) of environmental samples collected, compared with 34% (98 of 294) of samples collected during the same period in 2014. The quality and scope of polio eradication activities improved considerably following the establishment of a national Emergency Operations Center, which coordinated polio eradication partners' activities. All activities are following a National Polio Eradication Emergency Action Plan (4) that includes a rigorous action plan for the polio low transmission season (January-April). The presence of WPV1 in environmental samples in areas where no polio cases are detected highlights the need to improve surveillance for acute flaccid paralysis (AFP). Focused efforts to close remaining immunity gaps by locating, tracking, and vaccinating continually missed children and improving coverage with OPV through the routine vaccination program are needed to stop WPV transmission in Pakistan. |
Progress towards poliomyelitis eradication: Afghanistan, January 2014-August 2015
Chukwuma M , Saatcioglu A , Tangermann RH , Hadler S , Ehrhardt D . Wkly Epidemiol Rec 2015 90 (43) 581-8 Despite recent progress towards global polio eradication, endemic transmission of wild poliovirus type 1 | (WPV1) continues in Afghanistan and Pakistan.1, 2 The Afghanistan programme will need to overcome many | challenges to remain on track towards achieving the | objectives set in the 2013–2018 Strategic Plan of the | Global Polio Eradication Initiative.3 | Cross-border | transmission of WPV1 continues to occur to and from | Pakistan.4 | The country’s routine immunization system | remains weak and unable to reach recommended | benchmarks in most regions; hence, the national Polio | Eradication Initiative relies mainly on targeting children aged <5 years with supplementary oral polio | vaccine (OPV) immunization activities (SIAs). Due to | ongoing conflict and insecurity, some children continue | to be missed during SIAs in areas that are not under | government control; however, the majority of children | are still missed during SIAs in accessible areas, due to | failure to plan, implement and supervise efficient SIAs. |
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