Progress Toward Poliomyelitis Eradication --- Afghanistan and Pakistan, 2009

Afghanistan, Pakistan, India, and Nigeria are the four remaining countries where indigenous wild poliovirus (WPV) transmission has never been interrupted (1). This report updates previous reports (1,2) and describes polio eradication activities in Afghanistan and Pakistan during January--December 2009 and proposed activities in 2010 to address challenges. During 2009, both countries continued to conduct coordinated supplemental immunization activities (SIAs) and used multiple strategies to reach previously unreached children. These strategies included 1) use of short interval additional dose (SIAD) SIAs to administer a dose of oral poliovirus vaccine (OPV) within 1--2 weeks after a prior dose during negotiated periods of security; 2) systematic engagement of local leaders; 3) negotiations with conflict parties; and 4) increased engagement of nongovernmental organizations delivering basic health services. However, security problems continued to limit access by vaccination teams to large numbers of children. In Afghanistan, poliovirus transmission during 2009 predominantly occurred in 12 high-risk districts in the conflict-affected South Region; 38 WPV cases were confirmed in 2009, compared with 31 in 2008. In Pakistan, 89 WPV cases were confirmed in 2009, compared with 118 in 2008, but transmission persisted both in security-compromised areas and in accessible areas, where managerial and operational problems continued to affect immunization coverage. Continued efforts to enhance safe access of vaccination teams in insecure areas will be required for further progress toward interruption of WPV transmission in Afghanistan and Pakistan. In addition, substantial improvements in subnational accountability and oversight are needed to improve immunization activities in Pakistan.

Immunization Activities

Reported routine vaccination coverage of infants with 3 OPV doses (OPV3) in 2009 was 85% nationally in Afghanistan and 81% in Pakistan (3). However, acute flaccid paralysis (AFP) surveillance data* suggest that actual routine OPV3 coverage was much lower nationally and varied widely by subnational level in both countries. Based on 2009 AFP surveillance data, routine OPV3 coverage among children aged 6--23 months with nonpolio AFP was 63% nationally in Afghanistan (13% in the South Region and 76% in the rest of the country) and 61% nationally in Pakistan (69% in Punjab Province, 50% in Northwest Frontier Province [NWFP] and the Federally Administered Tribal Areas [FATA], 52% in Sindh Province, and 23% in Balochistan Province).

During 2009, large-scale house-to-house SIAs† targeting children aged <5 years using different formulations of OPV, depending on the epidemiologic situation, continued in both countries (Table 1). OPV formulations included trivalent (tOPV), monovalent type 1 (mOPV1) and type 3 (mOPV3), or OPV bivalent types 1 and 3 (bOPV).§ Afghanistan conducted six national immunization days (NIDs); four subnational immunization days (SNIDs) in the East, Southeast, and South regions along the border with Pakistan, three of which targeted nearly 50% of the national population of children aged <5 years; and four smaller-scale SIAD¶ SIAs after a preceding larger SIA, targeting children in conflict-affected areas of the South Region. Pakistan conducted six NIDs; four SNIDs in the main WPV transmission areas of NWFP/FATA, southern Punjab, and Sindh (including Karachi city), targeting 40%--50% of the national population aged <5 years; and four SIAD SIAs in conflict-affected areas of NWFP/FATA. These included two SIAD SIAs in Swat Valley, targeting >370,000 children aged <5 years, conducted after 1 year of civil conflict that prevented any polio vaccination.

In 2009, as in past years, certain vaccination campaigns were unable to reach children aged <5 years living in areas inaccessible** because of security problems. During 2009, the estimated percentage of children aged <5 years who were living in inaccessible areas in the South Region of Afghanistan ranged from >20% during SIAs conducted in January and March to 5% during the July and September SIAs. In Pakistan, the percentage of children aged <5 years who were living in SIA-inaccessible areas of NWFP increased from 10% in January to 20% in May and July, and then decreased to <5% in October and November. However, in FATA itself, the estimated percentage of children aged <5 years living in inaccessible areas increased from 15% in January to 30% by November.

AFP Surveillance

In 2009, AFP surveillance performance indicators remained high in both countries, including in areas with ongoing WPV transmission.†† The annual national nonpolio AFP rate (per 100,000 population aged <15 years) was 8.5 in Afghanistan (range among the eight regions: 6.7--12.0) and 6.1 in Pakistan (range among the six provinces/territories: 2.9--9.2). The percentage of nonpolio AFP cases for which adequate specimens were collected was 93% in Afghanistan (range: 81%--97%) and 90% in Pakistan (range: 83%--96%) (Table 2).

The polio laboratory at the National Institutes of Health (NIH) in Islamabad provides laboratory support for AFP surveillance in both countries, including genomic sequencing of poliovirus isolates. During 2009, the NIH laboratory processed 3,779 stool specimens from Afghanistan and 11,501 stool specimens from Pakistan. In 2009, to supplement AFP surveillance, Pakistan initiated weekly sewage sample collection in Lahore, Punjab Province, and Karachi, Sindh Province, to test for polioviruses.

WPV Incidence

In Afghanistan, 38 WPV cases (15 WPV1 and 23 WPV3) were reported during 2009, compared with 31 WPV cases (25 WPV1 and six WPV3) in 2008 (Figure, Table 2). During 2009, a total of 26 (68%) WPV cases were among children aged <36 months; nine (24%) had received no OPV doses; 12 (32%) had received 1--3 OPV doses, and 17 (44%) had received ≥4 OPV doses. WPV cases were found in 16 (5%) of 325 districts in Afghanistan during 2009 and 2008, of which 12 and 13 were found in the South Region, respectively, including eight districts with confirmed WPV cases during both years.

In Pakistan, 89 WPV cases (60 WPV1, 28 WPV3, and one WPV1/WPV3 mixed infection) were reported in 2009, compared with 118 cases (81 WPV1 and 37 WPV3) during 2008 (Figure, Table 2). During 2009, a total of 81 (91%) WPV cases were among children aged <36 months; 32 (36%) had received no OPV doses; 18 (20%) had received 1--3 OPV doses, and 39 (44%) had received ≥4 OPV doses. Of the 32 zero-dose cases, 22 (69%) came from only two repeatedly inaccessible areas, Swat Valley District and Bajour Agency. WPV cases were found in 34 (25%) of 135 districts in Pakistan during 2009, compared with 49 (36%) districts in 2008.

WPV genomic sequencing data from 2009 indicated continued endemic WPV circulation in two main transmission zones of both countries. In the northern transmission zone, which includes most of NWFP and FATA in Pakistan and bordering areas in eastern Afghanistan (Figure), 52 WPV cases (35 WPV1 and 17 WPV3) were reported during 2009. In the southern transmission zone, which extends from the West and South regions of Afghanistan into Pakistan through Balochistan and southern Punjab into Sindh, including persistently affected districts in the Quetta area§§ and several towns in Karachi, 58 cases (25 WPV1 and 33 WPV3) were reported during 2009. In addition, 17 WPV1 cases were reported throughout Punjab Province during 2009, most of which represented continuation of a 2008 outbreak in northern Punjab (4). In addition to determining the origin and transmission zones of circulating WPV, genomic sequencing of polioviruses obtained from AFP cases and sewage samples also found polioviruses not closely related to other viruses. Because genetic sequences of polioviruses generally are highly related in sensitive surveillance systems, the detection of these distantly related viruses indicates missed detection of WPV cases and suggests that performance indicators are not revealing surveillance weaknesses in some subnational areas.

Reported by

World Health Organization (WHO) Eastern Mediterranean Regional Office, Cairo, Egypt; WHO Afghanistan, Kabul; WHO Pakistan, Islamabad; Polio Eradication Dept, WHO, Geneva, Switzerland. Global Immunization Div, Div of Viral Diseases, National Center for Immunization and Respiratory Diseases, CDC.

Editorial Note

During 2009, the total number of WPV cases reported in Afghanistan and Pakistan did not substantially change compared with 2008, and both WPV1 and WPV3 serotypes continued to circulate in the same two shared transmission zones of both countries as in 2008. However, WPV transmission remained largely limited to previously affected districts of both countries. Additionally, some improvement was made toward the end of 2009 in decreasing the proportion of children in inaccessible districts of both countries, primarily in Afghanistan.

In Afghanistan, WPV transmission during the past 5 years has remained largely restricted to 12 insecure districts in the South Region. Since 2008, multiple strategies have been implemented to immunize these children. As a result, the proportion of children in the South Region who are not vaccinated in a given SIA was reduced to 5% of the overall target population toward the end of 2009. Meanwhile, Afghanistan has been able to keep most of the country free of endemic WPV transmission despite extensive population movements due to economic, social/cultural, and security reasons.

In Pakistan, circulation of both WPV serotypes persists in both transmission zones, with WPV repeatedly occurring, primarily in nine districts during the past 5 years. In the northern zone, WPV transmission continues because of limited access to children during SIAs in insecure areas of NWFP and FATA. Large-scale population movements from NWFP and FATA have caused renewed WPV transmission in polio-free areas. Access to districts in NWFP improved during the last quarter of 2009, but access into FATA deteriorated. In the southern zone, WPV circulation continued mainly due to weak routine vaccination programs and managerial and operational gaps during SIAs, compounded by large-scale population movements from insecure areas in southern Afghanistan. Substantial improvements in subnational accountability and oversight are needed to improve the quality of immunization activities in Pakistan.

During 2010, planning, resources, and immunization activities need to focus on the small number of persistently affected districts in Afghanistan and Pakistan. In insecure areas, negotiations with community leaders need to be enhanced, and efforts are needed to achieve agreement of all parties to conflict regarding Days of Tranquility during SIAs to ensure access to the target population of children aged <5 years and the safety of vaccination teams. Negotiations with conflict parties have been and will be supported by the International Federation of Red Cross and Red Crescent Societies. Coordination of both SIAs and AFP surveillance between both countries also needs to be strengthened further to interrupt transmission from cross-border movements. In addition, specific mechanisms need to be established to hold provincial, district, and local administrative leaders accountable for program performance.

References

1. CDC. Progress toward interruption of wild poliovirus transmission---worldwide, 2008. MMWR 2009;58:308--12.
2. CDC. Progress toward poliomyelitis eradication---Afghanistan and Pakistan, 2008. MMWR 2009;58:198--201.
3. World Health Organization. WHO vaccine-preventable diseases monitoring system: 2009 global summary. Geneva, Switzerland: World Health Organization. Available at http://www.who.int/vaccines/globalsummary/immunization/countryprofileselect.cfm. Accessed March 1, 2010.
4. Mushtaq MU, Majrooh MA, Ullah MZ, et al. Are we doing enough? Evaluation of the Polio Eradication Initiative in a district of Pakistan's Punjab province: a LQAS study. BMC Public Health 2010;10:60.

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