Progress Toward Poliomyelitis Eradication — Afghanistan, January 2014–August 2015

Chukwuma Mbaeyi, DDS1; Akif Saatcioglu, MD2; Rudolf H. Tangermann, MD2; Stephen Hadler, MD3; Derek Ehrhardt, MPH, MSN1

Despite recent progress toward global polio eradication, endemic transmission of wild poliovirus (WPV) continues to be reported in Afghanistan and Pakistan (1,2). The Afghanistan program must overcome many challenges to remain on track toward achieving the objectives set in the 2013–2018 strategic plan of the Global Polio Eradication Initiative (GPEI) (3). Cross-border transmission of WPV type 1 (WPV1) continues to occur among children traveling 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 (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 (5,6). 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.

Immunization Activities

Estimated national routine vaccination coverage of infants with 3 doses of oral poliovirus vaccine (OPV3) was 75% in Afghanistan in 2014, compared with 70% in 2013 (7). The proportion of nonpolio acute flaccid paralysis (NPAFP)† cases in children aged 6‒23 months who were reported to have received ≥3 doses of OPV, which is a proxy indicator for routine OPV3 coverage, was 64% nationally in 2014, with wide regional variation: 24% in the conflict-affected Southern Region, 50% in the Southeastern Region, 63% in the Western Region, and >70% in the other five regions. The proportion of children aged 6‒23 months with NPAFP who never received OPV either through routine immunization services or SIAs (i.e., "zero-dose" children) was <1% nationally during 2014.

During January 2014‒August 2015, house-to-house SIAs in Afghanistan targeted children aged <5 years, using different OPV formulations, including trivalent (types 1, 2, and 3), bivalent (types 1 and 3), and monovalent (type 1) OPV. During this period, 41 SIAs were conducted using OPV, including seven national immunization days (NIDs), six subnational immunization days (SNIDs), and 28 short-interval, additional dose, case-response campaigns.§ Additionally, vaccination campaigns were conducted using injectable inactivated poliovirus vaccine (IPV) in selected parts of districts at high risk for polio transmission in the Southern and Eastern regions after having gained access during November 2014 and February and August 2015. Vaccination campaigns were also implemented at transit points and border crossings with Pakistan as well as in camps for displaced persons.

Ongoing conflict and insecurity continue to limit access to children during SIAs, especially in parts of the Southern and Eastern regions, as well as in Farah Province of the Western Region. During NIDs conducted in 2015, estimates of children living in temporarily inaccessible areas¶ ranged from 1% to 3% of approximately 9 million children aged <5 years. SIAs in the Southern Region were further hampered by temporary bans imposed by local antigovernment groups in the provinces of Helmand (March‒July 2014 and December 2014‒January 2015) and Kandahar (June‒early August 2015). However, administrative coverage and postcampaign monitoring data of NIDs and SNIDs conducted in 2015 show that a majority of children not reached during SIAs live in accessible areas. Data from NIDs conducted in March 2015 suggest that 538,412 (7%) of 7,607,067 children targeted during the SIA were unvaccinated, among whom only 109,017 (20%) were living in inaccessible areas. During NIDs conducted in May and August 2015, the proportion of children missed because of inaccessibility were 32% and 14%, respectively. During these campaigns, approximately 400,000‒500,000 missed children lived in accessible areas.

Lot quality assurance sampling (LQAS),** which is used to assess the quality of SIAs (8), indicates that improvements noted in 2014 appear to have eroded slightly in 2015. SIAs in approximately one third of districts assessed were deemed unsatisfactory, with only 66%‒68% of districts achieving the desired pass threshold of ≥80% to date in 2015, compared with 70%‒77% of districts during the same period in 2014.

Poliovirus Surveillance

Acute Flaccid Paralysis (AFP) Surveillance. In 2014, the annual national NPAFP rate was 12.6 per 100,000 population aged <15 years (regional range = 9.1‒15.5) (Table). The percentage of AFP cases for which adequate stool specimens were collected was 92% (regional range = 82%‒98%). Six AFP cases reported from five provinces were classified as polio-compatible, including one case each reported from Farah, Helmand, Kandahar, and Kunar, and two cases reported from Uruzgan. These compatible cases indicate that gaps in surveillance quality remain, despite strong overall AFP surveillance performance indicators.††

Environmental Surveillance. Supplemental surveillance for polioviruses through sewage sampling began in Afghanistan in September 2013. Environmental surveillance is currently taking place at 13 sites in five provinces (Kandahar and Helmand in the Southern Region, Nangarhar and Kunar in the Eastern Region, and Kabul City in the Central Region). WPV1 was first isolated from sewage samples in July 2014. Since then, a total of 25 specimens from seven sites were positive for WPV1. In 2014, a total of 18 (19%) of 97 sewage specimens tested positive for WPV1. To date, only seven (8%) of 93 specimens have tested positive in 2015. WPV1 was most recently detected in sewage samples taken from Helmand Province in April 2015. WPV3 has not been detected in sewage samples since environmental surveillance began in Afghanistan.

Epidemiology of WPV and Vaccine-Derived Poliovirus (VDPV)

A total of 28 WPV1 cases were reported in 2014, compared with 14 cases in 2013; nine cases were reported during January‒August 2015, the same number reported during the same period in 2014 (Figure 1, Figure 2, Table). During this period, WPV1 cases were reported from 19 (5%) of 399 districts in Afghanistan. Among the WPV1 cases reported in 2014, three cases occurred in children who were displaced from North Waziristan in neighboring Pakistan, whereas nearly half (13 of 28) were reported from Kandahar Province in the Southern Region as part of an outbreak that began in September 2014. Of the nine WPV1 cases reported so far in 2015, four occurred in the security-compromised Farah Province of the Western Region, two were reported from Nangarhar Province (Eastern Region), whereas Hirat Province (Western Region), Helmand Province and Nimroz Province (Southern Region) each reported one case. Of the 37 WPV1 cases reported during January 2014‒August 2015, 26 (70%) were reported among children aged <36 months. Among these 26 children, eight (31%) had never received OPV, one (4%) had received a single dose, and 12 (46%) had received >4 doses. Eight of the nine WPV1 cases thus far reported during 2015 were in children who never received OPV through routine immunization services regardless of age.

Based on genomic sequencing, 26 of 28 WPV1 cases detected in 2014 belong to the R4B cluster known to be also circulating in neighboring areas of Pakistan; of the two remaining cases, one (Laghman Province, Eastern Region) belonged to the R4A cluster, believed to have originated in Pakistan, and the other (Kandahar Province, Southern Region) belonged to the R2A cluster, considered indigenous to Afghanistan (9). The seven cases reported from the Western and Southern regions in 2015 belong to the R4B cluster that spread from Kandahar in late 2014; the two cases from Nangarhar are closely matched and likely linked to cross-border importation from Pakistan. No polio cases attributable to WPV3 or circulating VDPV§§ have been detected in Afghanistan since April 2010 and March 2013, respectively.

Discussion

Afghanistan experienced a major setback in its progress towards the eradication of polio during the period under review. After having come close to interrupting indigenous transmission of WPV during 2013 (5), Afghanistan saw a resurgence in poliovirus transmission in 2014, as the number of cases doubled from levels reported in the previous year. Thus far in 2015, few cases have been reported, similar to the pattern observed during the comparable low transmission season of 2014. However, as the high transmission season approaches, there is cause for concern regarding the feasibility of interrupting transmission within a year, given ongoing WPV circulation in areas with known immunity gaps (i.e., areas with suboptimal routine or SIA OPV coverage) in the Southern, Eastern, and Western regions.

Although there are encouraging signs in the endemic transmission areas of the Southern Region, with no cases reported from Kandahar, and only a single case reported from each of Helmand and Nimroz provinces in 2015, vulnerabilities remain. The neighboring Farah Province in the Western Region has accounted for nearly half of the cases reported in 2015, frequently involving unvaccinated children. High levels of population movement between the Western and Southern regions provide ample opportunities for transmission between districts in the two regions. Data from short-interval, additional dose, case-response campaigns and routine immunization activities indicate the persistence of immunity gaps in both regions. Despite a small improvement in estimated OPV3 coverage nationally in 2014, routine immunization remained low in both the Southern and Western regions. Obstacles to achieving optimal routine immunization coverage in these regions are largely related to insecurity, poor infrastructure, and limited access to health services.

LQAS results indicate that the overall quality of vaccination campaigns in 2015 has declined slightly compared with 2014, with considerable numbers of children who live in accessible areas being missed during campaigns. Improving the quality of SIAs will require better preparation through proper staff training and detailed microplanning, and then ensuring adequate monitoring and supervision during the course of campaigns. Additionally, innovative approaches adopted in the National Emergency Action Plan to reach and vaccinate more children should be consistently implemented and regularly evaluated for effectiveness. These approaches include assignment of permanent polio teams that conduct regular house-to-house visits for polio vaccination to low-performing districts,¶¶ use of permanent transit teams to vaccinate children at busy transit points close to inaccessible areas, and more recently, implementation of a strategy to record, revisit, and vaccinate children not at home during the initial house visit. Negotiations with local authorities and persons of influence in insecure and conflict-affected areas with limited or no access during SIAs should continue while ensuring that the polio program maintains its neutrality. Cross-border coordination with neighboring Pakistan must remain a top priority, including the continued use of permanent transit teams to vaccinate children moving across the border in both directions.

The establishment of a national polio EOC in Nigeria played a crucial role in the country's successful elimination of indigenous poliovirus transmission (10). Hence, the national PEI in Afghanistan will stand to benefit from establishing polio EOCs nationally and in critical regions to improve overall coordination of polio eradication activities. In addition, with the updated and strengthened National Emergency Action Plan having been finalized to address key vulnerabilities, the government of Afghanistan must demonstrate the high levels of commitment needed to interrupt indigenous poliovirus transmission. This commitment must translate into urgent action that will make the goal of global polio eradication a reality.

Acknowledgments

Becky Maholland, Office of Public Health Preparedness and Response, CDC; World Health Organization Global Polio Laboratory Network.

1Global Immunization Division, Center for Global Health, CDC;2 Polio Eradication Department, World Health Organization; 3Division of Bacterial Diseases, National Center for Immunization and Respiratory Diseases, CDC.

Corresponding author: Chukwuma Mbaeyi, cmbaeyi@cdc.gov, 404-823-7764.

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