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In 1996, China adopted a virological classification of acute flaccid paralysis (AFP) cases for its surveillance system. Only AFP cases with wild poliovirus in stool specimens are confirmed as polio. Cases with adequate stool specimens that are negative for wild poliovirus are not counted. This paper describes a methodology to rule out poliomyelitis in AFP cases with inadequate stool specimens. National surveillance data were analysed using dot maps to detect clusters of AFP cases with high-risk factors for poliomyelitis. The surveillance system and vaccine coverage were assessed during field investigations. Four clusters of AFP cases were identified, but no poliomyelitis cases. Programmatic failures in the identified high-risk areas included low vaccination rates, poor stool specimen collection and inadequate AFP surveillance. Programme strategies were implemented to correct the identified failures. Use of this methodology provides strong evidence consistent with the absence of wild poliovirus in China.

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Ten years after the year 2000 target was set by the World Health Assembly, the global poliomyelitis eradication effort has made significant progress towards that goal. The success of the initiative is built on political commitment within the endemic countries. A partnership of international organizations and donor countries works to support the work of the countries. Interagency coordinating committees are used to ensure that all country needs are met and to avoid duplication of donor effort. Private sector support has greatly expanded the resources available at both the national and international level. At the programmatic level, rapid implementation of surveillance is the key to success, but the difficulty of building effective surveillance programmes is often underestimated. Mass immunization campaigns must be carefully planned with resources mobilized well in advance. Programme strategies should be simple, clear and concise. While improvements in strategy and technology should be continuously sought, changes should be introduced only after careful consideration. Careful consideration should be given in the planning phases of a disease control initiative on how the initiative can be used to support other health initiatives.

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Polio eradication activities in the Western Pacific Region (WPR) have reduced the transmission of wild poliovirus to one remaining focus of endemic transmission in the Mekong Delta area of South Vietnam and Cambodia. There has been a high level of government commitment for national immunization days in all WPR countries in which poliomyelitis was previously endemic and for continuous improvement in acute flaccid paralysis (AFP) surveillance quality. The total number of reported confirmed poliomyelitis cases in 1995 (as of June 1996) was 432, only 7% of the total of 5825 cases reported in 1990. In 1995, wild poliovirus was isolated from only 19 of 4800 AFP patients from whom specimens were collected and analyzed. There has been one importation of wild poliovirus type 1 into China from a neighboring country. An international Regional Commission for the Certification of Poliomyelitis Eradication in the WPR has been formed and met for the first time in April 1996.

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A multitiered network of polio laboratories, consisting of specialized reference laboratories, regional reference laboratories, national laboratories and, in the case of China, provincial laboratories, was established in the Western Pacific Region of the World Health Organization (WHO) in 1992. The network currently consists of 43 laboratories within the Region and is coordinated through the WHO Regional Office in Manila. As the levels and extent of supplementary immunization and acute flaccid paralysis surveillance activities have increased, so has the work load of network laboratories. The total number of stool specimens collected and processed in Polio Laboratory Network laboratories in this WHO region in 1995 exceeded 15,000. With the Region now establishing the criteria necessary for certification of polio-free status, it is essential for the Polio Laboratory Network to establish international confidence in its ability to carry out its role in the eradication of polio.

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The implementation of the World Health Organization's recommended strategies for polio eradication, particularly acute flaccid paralysis (AFP) surveillance, can be limited by difficult circumstances beyond the control of immunization personnel. In Cambodia, however, obstacles to establishing AFP surveillance were rapidly overcome using a strategy that improved reporting through active surveillance in a geographically limited area before gradually expanding to include the whole country. The success of the strategy was ensured by the timely provision of the resources that were needed to establish, expand, and monitor surveillance activities.

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Experience with national immunization days (NIDs) in six countries of the Western Pacific Region has shown that political support at all levels, detailed logistics plans, strategies appropriate to the local situation, and simple social mobilization messages have been key factors in the success of NIDs. Conventional strategies that may apply to conducting routine Expanded Programme on Immunization vaccinations do not necessarily apply to NIDs, in which the maximum number of children must be immunized in 1 or 2 days. Setting up temporary immunization posts at sites convenient to the local situation, moving the posts once or twice during the course of a day, and using volunteers to staff them are among many of the adaptations used successfully. Coverage figures published immediately after an NID can be misleading because of uncertainty about the true denominator. The true measure of the success of NIDs is in surveillance for wild poliovirus after the event.

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Infant immunization coverage in the Western Pacific Region of the World Health Organization was reviewed to evaluate the impact of polio eradication activities on routine immunization services. The trend in bacille Calmette-Guérin (one dose; BCG), diphtheria-tetanus toxoids-pertussis (three doses; DTP3), and measles (one dose) vaccination rates was analyzed from the beginning of eradication activities in 1990 to 1994 in the five polio-endemic countries that conducted supplementary oral polio vaccine immunization. In China and the Philippines, coverage for each antigen remained at or above 90% and 85%, respectively, while in Vietnam, coverage for all three antigens rose from 85% to 95%. BCG, DTP3, and measles vaccine coverage more than doubled in the People's Democratic Republic of Lao and increased by >30% in the Kingdom of Cambodia during the same period.

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