Insecurity, polio vaccination rates, and polio incidence in northwest Pakistan.

Pakistan is one of three countries in which endemic transmission of poliovirus has never been stopped. Insecurity is often cited but poorly studied as a barrier to eradicating polio. We analyzed routinely collected health data from 32 districts of northwest Pakistan and constructed an index of insecurity based on journalistic reports of the monthly number of deaths and injuries resulting from conflict-related security incidents. The primary outcomes were the monthly incidence of paralytic polio cases within each district between 2007 and 2014 and the polio vaccination percentage from 666 district-level vaccination campaigns between 2007 and 2009, targeting ∼5.7 million children. Multilevel Poisson regression controlling for time and district fixed effects was used to model the association between insecurity, vaccinator access, vaccination rates, and polio incidence. The number of children inaccessible to vaccinators was 19.7% greater (95% CI: 19.2-20.2%), and vaccination rates were 5.3% lower (95% CI: 5.2-5.3%) in "high-insecurity" campaigns compared with "secure" campaigns. The unadjusted mean vaccination rate was 96.3% (SD = 8.6) in secure campaigns and 88.3% (SD = 19.2) in high-insecurity campaigns. Polio incidence was 73.0% greater (95% CI: 30-131%) during high-insecurity months (unadjusted mean = 0.13 cases per million people, SD = 0.71) compared with secure months (unadjusted mean = 1.23 cases per million people, SD = 4.28). Thus, insecurity was associated with reduced vaccinator access, reduced polio vaccination, and increased polio incidence in northwest Pakistan. These findings demonstrate that insecurity is an important obstacle to global polio eradication.

National, Regional and Global Certification Bodies for Polio Eradication: A Framework for Verifying Measles Elimination.

The Global Certification Commission (GCC), Regional Certification Commissions (RCCs), and National Certification Committees (NCCs) provide a framework of independent bodies to assist the Global Polio Eradication Initiative (GPEI) in certifying and maintaining polio eradication in a standardized, ongoing, and credible manner. Their members meet regularly to comprehensively review population immunity, surveillance, laboratory, and other data to assess polio status in the country (NCC), World Health Organization (WHO) region (RCC), or globally (GCC). These highly visible bodies provide a framework to be replicated to independently verify measles and rubella elimination in the regions and globally.

Using Acute Flaccid Paralysis Surveillance as a Platform for Vaccine-Preventable Disease Surveillance.

Surveillance for acute flaccid paralysis (AFP) is a fundamental cornerstone of the global polio eradication initiative (GPEI). Active surveillance (with visits to health facilities) is a critical strategy of AFP surveillance systems for highly sensitive and timely detection of cases. Because of the extensive resources devoted to AFP surveillance, multiple opportunities exist for additional diseases to be added using GPEI assets, particularly because there is generally 1 district officer responsible for all disease surveillance. For this reason, integrated surveillance has become a standard practice in many countries, ranging from adding surveillance for measles and rubella to integrated disease surveillance for outbreak-prone diseases (integrated disease surveillance and response). This report outlines the current level of disease surveillance integration in 3 countries (Nepal, India, and Nigeria) and proposes that resources continue for long-term maintenance in resource-poor countries of AFP surveillance as a platform for surveillance of vaccine-preventable diseases and other outbreak-prone diseases.

Lessons Learned and Legacy of the Stop Transmission of Polio Program.

In 1988, the by the World Health Assembly established the Global Polio Eradication Initiative, which consisted of a partnership among the World Health Organization (WHO), Rotary International, the Centers for Disease Control and Prevention (CDC), and the United Nations Children's Fund. By 2016, the annual incidence of polio had decreased by >99.9%, compared with 1988, and at the time of writing, only 3 countries in which wild poliovirus circulation has never been interrupted remain: Afghanistan, Nigeria, and Pakistan. A key strategy for polio eradication has been the development of a skilled and deployable workforce to implement eradication activities across the globe. In 1999, the Stop Transmission of Polio (STOP) program was developed and initiated by the CDC, in collaboration with the WHO, to train and mobilize additional human resources to provide technical assistance to polio-endemic countries. STOP has also informed the development of other public health workforce capacity to support polio eradication efforts, including national STOP programs. In addition, the program has diversified to address measles and rubella elimination, data management and quality, and strengthening routine immunization programs. This article describes the STOP program and how it has contributed to polio eradication by building global public health workforce capacity.

The critical role of acute flaccid paralysis surveillance in the Global Polio Eradication Initiative.

Acute flaccid paralysis (AFP) surveillance is a key strategy used by the Global Polio Eradication Initiative (GPEI) to measure progress towards reaching the global eradication goal. Supported by a global polio laboratory network, AFP surveillance is conducted in 179 of 194 WHO member states. Active surveillance visits to priority health facilities are used to assure all children <15 years with AFP are detected, followed by stool specimen collection and testing for poliovirus in WHO-accredited polio laboratories. The quality of AFP surveillance is regularly monitored with standardized surveillance quality indicators. In highest risk countries and areas, the sensitivity of AFP surveillance is enhanced by environmental surveillance (testing of sewage samples). Genetic sequencing of detected poliovirus isolates yields programmatically important information on polio transmission pathways. AFP surveillance is one of the most valuable assets of the GPEI, with the potential to serve as a platform to build integrated disease surveillance systems. Continued support to maintain AFP surveillance systems will be essential, to reliably monitor the completion of global polio eradication, and to assure that a key resource for building surveillance capacity is transitioned post-eradication to support other health priorities.

Progress Toward Poliomyelitis Eradication - Afghanistan, January 2015‒August 2016.

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 2015‒August 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 January‒August 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 Plan† 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.

Progress Toward Polio Eradication - Worldwide, 2015-2016.

In 1988, the World Health Assembly resolved to eradicate poliomyelitis. Wild poliovirus (WPV) transmission persists in only two countries (Afghanistan and Pakistan) after the removal of Nigeria from the list of countries with endemic polio in September 2015.* Indigenous WPV type 2 has not been detected since 1999 and was declared eradicated by the Global Commission for the Certification of Poliomyelitis Eradication in September 2015.(†) Since November 2012, when the last case of WPV type 3 was detected in Nigeria, WPV type 1 has been the sole circulating type of WPV (1). This report summarizes global progress toward polio eradication during 2015-2016 and updates previous reports (2). In 2015, 74 WPV cases were reported in two countries (Afghanistan and Pakistan), a decrease of 79% from the 359 WPV cases reported in 2014 in nine countries; 12 WPV cases have been reported in 2016 (to date), compared with 23 during the same period in 2015 (3). Paralytic polio caused by circulating vaccine-derived poliovirus (cVDPV) remains a risk in areas with low oral poliovirus vaccine (OPV) coverage. Seven countries, including Pakistan, reported 32 cVDPV cases in 2015 (4). In four of these countries, ≥6 months have passed since the most recent case or isolate. One country (Laos) with VDPV transmission in 2015 has reported three additional cVDPV cases in 2016 to date. Encouraging progress toward polio eradication has been made over the last year; however, interruption of WPV transmission will require focus on reaching and vaccinating every missed child through high quality supplementary immunization activities (SIAs) and cross-border coordination between Afghanistan and Pakistan (5,6).

Notes from the Field: Circulating Vaccine-Derived Poliovirus Outbreaks - Five Countries, 2014-2015.

In 2015, wild poliovirus (WPV) transmission was identified in only Afghanistan and Pakistan (1). The widespread use of live, attenuated oral poliovirus vaccine (OPV) has been key in polio eradication efforts. However, OPV use, particularly in areas with low vaccination coverage, is associated with the low risk for emergence of vaccine-derived polioviruses (VDPV), which can cause paralysis (2). VDPVs vary genetically from vaccine viruses and can cause outbreaks in areas with low vaccination coverage. Circulating VDPVs (cVDPVs) are VDPVs in confirmed outbreaks. Single VDPVs for which the origin cannot be determined are classified as ambiguous (aVDPVs), which can also cause paralysis. Among the three types of WPV, type 2 has been declared to be eradicated. More than 90% of cVDPV cases have been caused by type 2 cVDPVs (cVDPV2). Therefore, in April 2016, all OPV-using countries of the world are discontinuing use of type 2 Sabin vaccine by simultaneously switching from trivalent OPV (types 1, 2, and 3) to bivalent OPV (types 1 and 3) for routine and supplementary immunization. The World Health Organization recently broadened the definition of cVDPVs to include any VDPV with genetic evidence of prolonged transmission (i.e., >1.5 years) and indicated that any single VDPV2 event (a case of paralysis caused by a VDPV or isolation of a VDPV from an environmental specimen) should elicit a detailed outbreak investigation and local immunization response. A confirmed cVDPV2 detection should elicit a full poliovirus outbreak response that includes multiple supplemental immunization activities (SIAs); an aVDPV designation should be made only after investigation and response (3). Since 2005, there have been 1-8 cVDPV outbreaks and 3-12 aVDPV events per year. There are currently five active cVDPV outbreaks in Guinea, Laos, Madagascar, Myanmar, and Ukraine, and four other active VDPV events.

Progress Toward Poliomyelitis Eradication--Afghanistan, January 2014‒August 2015.

Despite recent progress toward global polio eradication, endemic transmission of wild poliovirus (WPV) continues to be reported in Afghanistan and Pakistan. The Afghanistan program must overcome many challenges to remain on track toward achieving the objectives set in the 2013­2018 strategic plan of the Global Polio Eradication Initiative (GPEI). Cross-border transmission of WPV type 1 (WPV1) continues to occur among children traveling to and from Pakistan. The country's routine immunization system remains weak and unable to reach recommended benchmarks in most regions; hence, the national Polio Eradication Initiative (PEI) relies mainly on providing children aged <5 years with oral poliovirus vaccine (OPV), administered during supplementary immunization activities (SIAs). Because of ongoing conflict and insecurity, some children continue to be missed during SIAs in areas not under government control; however, the majority of missed children live in accessible areas and are often unreached because of a failure to plan, implement, and supervise SIAs efficiently. This report describes polio eradication activities and progress in Afghanistan during January 2014‒August 2015 and updates previous reports. During 2014, a total of 28 WPV1 cases were reported in Afghanistan, compared with 14 cases in 2013; nine cases were reported during January‒August 2015, the same number as during the same period in 2014. To eliminate poliovirus transmission in Afghanistan, emergency operations centers (EOCs) need to be established at the national level and in critical regions without delay to improve overall coordination and oversight of polio eradication activities. The recently revised National Emergency Action Plan for polio eradication needs to be fully implemented, including detailed microplanning and enhanced monitoring and supervision of SIAs, as well as improved cross-border coordination with Pakistan.

Progress toward polio eradication - worldwide, 2014-2015.

In 1988, the World Health Assembly of the World Health Organization (WHO) resolved to eradicate polio worldwide. Wild poliovirus (WPV) transmission has been interrupted in all but three countries (Afghanistan, Nigeria, and Pakistan). No WPV type 2 cases have been detected worldwide since 1999, and the last WPV type 3 case was detected in Nigeria in November 2012; since 2012, only WPV type 1 has been detected. Circulating vaccine-derived poliovirus (cVDPV), usually type 2, continues to cause cases of paralytic polio in communities with low population immunity. In 2012, the World Health Assembly declared global polio eradication "a programmatic emergency for global public health", and in 2014, WHO declared the international spread of WPV to previously polio-free countries to be "a public health emergency of international concern". This report summarizes global progress toward polio eradication during 2014-2015 and updates previous reports. In 2014, a total of 359 WPV cases were reported in nine countries worldwide. Although reported WPV cases increased in Pakistan and Afghanistan, cases in Nigeria decreased substantially in 2014, and encouraging progress toward global WPV transmission interruption has occurred. Overcoming ongoing challenges to interruption of WPV transmission globally will require sustained programmatic enhancements, including improving the quality of supplementary immunization activities (SIAs) to interrupt transmission in Afghanistan and Pakistan and to prevent WPV exportation to polio-free countries.

Possible eradication of wild poliovirus type 3--worldwide, 2012.

In 1988, the World Health Assembly resolved to eradicate polio worldwide. Since then, four of the six World Health Organization (WHO) regions have been certified as polio-free: the Americas in 1994, the Western Pacific Region in 2000, the European Region in 2002, and the South-East Asia Region in 2014. Currently, nearly 80% of the world's population lives in areas certified as polio-free. Certification may be considered when ≥3 years have passed since the last isolation of wild poliovirus (WPV) in the presence of sensitive, certification-standard surveillance. Although regional eradication has been validated in the European Region and the Western Pacific Region, outbreaks resulting from WPV type 1 (WPV1) imported from known endemic areas were detected and controlled in these regions in 2010 and 2011, respectively. The last reported case associated with WPV type 2 (WPV2) was in India in 1999, marking global interruption of WPV2 transmission. The completion of polio eradication was declared a programmatic emergency for public health in 2012, and the international spread of WPV1 was declared a public health emergency of international concern in May 2014. The efforts needed to interrupt all indigenous WPV1 transmission are now being focused on the remaining endemic countries: Nigeria, Afghanistan, and Pakistan. WPV type 3 (WPV3) has not been detected in circulation since November 11, 2012. This report summarizes the evidence of possible global interruption of transmission of WPV3, based on surveillance for acute flaccid paralysis (AFP) and environmental surveillance.

Outbreaks of paralytic poliomyelitis during 1996-2012: the changing epidemiology of a disease in the final stages of eradication.

BACKGROUND: Despite substantial progress toward eradication of poliomyelitis, the risk of poliomyelitis outbreaks resulting from virus importations into polio-free areas persists. We reviewed the changing epidemiology of outbreaks in the final stages of the eradication initiative. METHODS: Available literature on outbreaks of poliomyelitis caused by wild polioviruses between 1996 and 2012 was reviewed. RESULTS: During this period, there were 22 outbreaks involving 39 countries. Outbreaks ranged in size from 1 to 1335 cases. These outbreaks caused 4571 cases, representing 21% of all cases reported during this period. Five outbreaks involved multiple countries. In 76% of outbreaks (16/21) with a known age distribution, cases concentrated among children aged <5 years; in 19% (4/21), most cases were among adolescents and adults. The outbreaks among adolescents and adults were associated with higher case-fatality ratios, ranging from 12% in Albania in 1994 to 41% in the Republic of Congo in 2010. The majority of outbreaks were controlled within 6 months with oral poliovirus vaccine. CONCLUSIONS: Importations resulting in epidemic transmission of wild poliovirus caused thousands of cases of paralysis often in countries where poliomyelitis had not occurred for many years. The changing epidemiology, with cases and higher case-fatality ratios among adults, increased the severity of these outbreaks.

Assessing and mitigating the risks for polio outbreaks in polio-free countries - Africa, 2013-2014.

Since 1988, when the Global Polio Eradication Initiative (GPEI) began, the annual number of polio cases has decreased by >99%. Only three countries remain that have never interrupted wild poliovirus (WPV) transmission: Afghanistan, Nigeria, and Pakistan. Since 2001, outbreaks have occurred in 31 formerly polio-free counties in Africa, with outbreaks in 25 countries caused by WPV originating in Nigeria (2-4). After the declaration of the World Health Assembly of polio eradication as a programmatic emergency in 2012, efforts to identify areas at high risk for importation-associated outbreaks and to reduce that risk have been intensified. This report updates the 2013 assessment of the risk for outbreaks attributable to importation of poliovirus in 33 countries in Africa, using indicators of childhood susceptibility to poliovirus and proximity to countries currently affected by polio . From January 2013 to August 12, 2014, outbreaks occurred in five African countries. Four of the five (Cameroon, Equatorial Guinea, Ethiopia, and Somalia) have had recent transmission (cases within the previous 12 months). Based on the current risk assessment, 15 countries are considered to be at high risk for WPV outbreaks, five at moderate-to-high risk, seven at moderate risk, and six at low risk. In 15 of the 33 countries, less than half of the population resides in areas where surveillance performance indicators have met minimum targets. Enhanced, coordinated activities to raise childhood immunity are underway in 2014 to prevent additional WPV spread. Although substantial progress toward polio eradication has occurred in Nigeria, all African countries remain at risk for outbreaks as long as WPV continues to circulate anywhere on the continent.

Progress toward polio eradication--Worldwide, 2013-2014.

In 1988, the World Health Assembly of the World Health Organization (WHO) resolved to interrupt wild poliovirus (WPV) transmission worldwide, and in 2012, the World Health Assembly declared the completion of global polio eradication a programmatic emergency for public health. By 2013, the annual number of WPV cases had decreased by >99% since 1988, and only three countries remained that had never interrupted WPV transmission: Afghanistan, Nigeria, and Pakistan. This report summarizes global progress toward polio eradication during 2013-2014 and updates previous reports. In 2013, a total of 416 WPV cases were reported globally from eight countries, an 86% increase from the 223 WPV cases reported from five countries in 2012. This upsurge in 2013 was caused by a 60% increase in WPV cases detected in Pakistan, and by outbreaks in five previously polio-free countries resulting from international spread of WPV. In 2014, as of May 20, a total of 82 WPV cases had been reported worldwide, compared with 34 cases during the same period in 2013. Polio cases caused by circulating vaccine-derived poliovirus (cVDPV) were detected in eight countries in 2013 and in two countries so far in 2014. To achieve polio eradication in the near future, further efforts are needed to 1) address health worker safety concerns in areas of armed conflict in priority countries, 2) to prevent further spread of WPV and new outbreaks after importation into polio-free countries, and 3) to strengthen surveillance globally. Based on the international spread of WPV to date in 2014, the WHO Director General has issued temporary recommendations to reduce further international exportation of WPV through vaccination of persons traveling from currently polio-affected countries.

Surveillance systems to track progress toward global polio eradication - worldwide, 2012-2013.

In 2012, the World Health Assembly of the World Health Organization (WHO) declared completion of polio eradication a programmatic emergency. Polio cases are detected through surveillance of acute flaccid paralysis (AFP) cases and subsequent testing of stool specimens for polioviruses (PVs) at WHO-accredited laboratories within the Global Polio Laboratory Network (GPLN). AFP surveillance is supplemented by environmental surveillance, testing sewage samples from selected sites for PVs. Virologic surveillance, including genomic sequencing to identify isolates by genotype and measure divergence between isolates, guides Global Polio Eradication Initiative (GPEI) activities by confirming the presence of PV, tracking chains of PV transmission, and highlighting gaps in AFP surveillance quality. This report provides AFP surveillance quality indicators at national and subnational levels during 2012-2013 for countries that experienced PV cases during 2009-2013 in the WHO African Region (AFR) and Eastern Mediterranean Region (EMR), the remaining polio-endemic regions. It also summarizes the results of environmental surveillance and reviews indicators assessing the timeliness of reporting of PV isolation and of virus strain characterization globally. Regional-level performance indicators for timely reporting of PV isolation were met in five of six WHO regions in 2012 and 2013. Of 30 AFR and EMR countries that experienced cases of PV (wild poliovirus [WPV], circulating vaccine-derived poliovirus [cVDPV], or both) during 2009-2013, national performance indicator targets for AFP surveillance and collection of adequate specimens were met in 27 (90%) countries in 2012 and 22 (73%) in 2013. In 17 (57%) countries, ≥80% of the population lived in subnational areas meeting both AFP performance indicators in 2012, decreasing to 13 (43%) in 2013. To achieve polio eradication and certify interruption of PV transmission, intensive efforts to strengthen and maintain AFP surveillance are needed at subnational levels, including in field investigation and prompt collection of specimens, particularly in countries with current or recent active PV transmission.

Certification of polio eradication: process and lessons learned.

Since the 1988 World Health Assembly resolution to eradicate poliomyelitis, considerable progress has been made towards interrupting the transmission of wild poliovirus globally. A formal process for the certification of polio eradication was established on the basis of experience gained during smallpox eradication. Independent groups of experts were designated at the global, regional, and country levels to conduct the process. The main requirements for the global certification of the eradication of wild poliovirus are the absence of wild poliovirus, isolated from suspect polio cases, healthy individuals, or environmental samples, in all WHO regions for a period of at least three years in the presence of high-quality, certification-standard surveillance and the containment of all wild poliovirus stocks in laboratories. Three WHO regions--the Region of the Americas (1994), Western Pacific Region (2000), and European Region (2002)--have already been certified free of indigenous wild poliovirus. Eradication and certification activities are progressing well in the three endemic regions (African, Eastern Mediterranean, and South-East Asia). Several challenges remain for the certification of polio eradication: the need for even closer coordination of certification activities between WHO regions, the verification of laboratory containment, the development of an appropriate mechanism to verify the absence of circulating vaccine-derived polioviruses in the future, and the maintenance of polio-free status in certified regions until global certification.