International Notes Progress Toward Poliomyelitis Eradication -- People's Republic of China, 1990-1994

In 1988, the Western Pacific Region of the World Health Organization (WHO) adopted a resolution to eradicate poliomyelitis from the region by the end of 1995. Since then, the People's Republic of China (1993 population: 1.2 billion) has made substantial progress toward the eradication of polio by initiating supplementary vaccination activities with oral poliovirus vaccine (OPV) in 1990. This report updates these efforts and describes the impact of China's first National Immunization Days (NIDs) * during 1993-1994 (1). National Immunization Days

During the first NIDs on December 5 and 6, 1993, and January 5 and 6, 1994, the numbers of children aged 0-47 months vaccinated in all 30 provinces in China were 82 million and 83 million, respectively. NIDs specifically targeted children with no previous history of OPV receipt. As a result, 31% of children aged less than 1 year, 6% of children aged 1 year, 4% of children aged 2 years, and 2% of children aged 3 years who were vaccinated during NIDs had not previously received OPV.

During September-October 1994, two rounds of additional supplemental vaccinations targeting all children aged less than 4 years were conducted in seven high-risk provinces in southern and western China where type 1 wild poliovirus was detected in 1993 (Fujian, Guangdong, Guizhou, Hainan, Qinghai, and Xinjiang) or where continued transmission was suspected (Yunnan). Provincewide vaccination rounds were conducted in Fujian, Guangdong, and Hainan, and in selected counties in the remaining provinces. However, of eight counties in Guizhou with a wild poliovirus isolated in 1993, five were not included in the supplemental vaccination rounds because of a shortage of funds. Surveillance for Polio

Eradication of disease requires a surveillance system that can detect a single case. China and many other polio-endemic countries have developed a system in which any case of acute flaccid paralysis (AFP) in a person aged less than 15 years is reported as a suspected case of polio. Effective AFP surveillance can detect an annual incidence of at least one case of AFP per 100,000 persons aged less than 15 years (2). Two stool specimens are collected from each suspected case at an interval of 24-48 hours to determine the presence of poliovirus; however, the standard WHO case definition ** permits an AFP case to be confirmed as polio if it meets any of four criteria, including the isolation of poliovirus from a stool specimen.

Following a nationwide outbreak during 1989-1990, reported cases of confirmed polio ** reached a historic low of 653 in 1993 Figure_1. Of 1818 persons reported with AFP in 1993, 64% had at least one stool specimen collected; wild polioviruses were isolated from 60 persons in five southern provinces (Fujian, Guangdong, one county in Hunan province bordering Guangdong, Hainan, and Guizhou) and two western provinces (Qinghai and Xinjiang). Among the 56 persons for whom age was known, 42 (75%) were children aged 0-23 months and 54 (96%) were children aged less than 4 years; among the 52 persons for whom vaccination status was known, 37 (71%) had received either no doses or one previous dose of OPV.

During January-October 1994, a provisional total of 114 cases of confirmed polio ** were reported; of 1234 persons reported with AFP, 72% had at least one stool specimen collected. During this period, one wild type 1 poliovirus was found in a child aged 1 year from Kashgar prefecture in Xinjiang autonomous region (province), with onset of paralysis on February 20, 1994.

The rate of reported AFP patients per 100,000 children aged less than 15 years increased from 0.3 in 1993 to 0.8 during January-September 1994. However, in 11 of 30 provinces, the rate of reported AFP cases per 100,000 children aged less than 15 years was less than 0.5, below the reference rate of greater than or equal to 1.0 per 100,000 children aged less than 15 years used to define a sensitive AFP surveillance system. In addition, the percentage of reported AFP patients with at least one stool specimen collected increased from 64% in 1993 to 72% in 1994. In 1994, 55% of AFP patients had one stool specimen collected within 0-14 days of onset of paralysis, and 44% had two stool specimens.

During January-October 1994, 23 contiguous provinces in China with a total population of 982 million persons reported no wild polioviruses. During this period, stool specimens from 2039 AFP patients were collected and tested for poliovirus. Reported by: B Yang, MD, H Li, MD, Div of Expanded Program on Immunization; Z Dai, MD, Z Wang, MD, Dept of Health and Epidemic Prevention, Ministry of Health; K Wang, MD, L Zhang, MD, R Zhang, MD, J Zhang, MD, T Jiang, X Zhang, MD, Chinese Academy of Preventive Medicine, Beijing, People's Republic of China. Expanded Program on Immunization Unit, Western Pacific Regional Office, World Health Organization, Manila, Philippines. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Polio Eradication Activity, National Immunization Program, CDC.

Editorial Note

Editorial Note: The findings in this report suggest that the NIDs in China during 1993-1994 were highly effective in reducing circulating wild poliovirus to low levels in China. Before the NIDs, wild poliovirus was documented in five southern provinces and two western provinces. Following the NIDs, wild poliovirus has been detected in only one prefecture in the remote western part of China. The decline in reported cases of polio and in the number of cases with wild poliovirus has occurred despite improvement in the sensitivity of surveillance. Collaborative efforts involving Rotary International, United Nations Children's Fund (UNICEF), and other private organizations and government agencies have been integral to the polio-eradication strategies in China.

Continued progress toward achieving polio eradication in China will require at least five strategies: 1) improving reporting of AFP patients to achieve a rate of greater than or equal to 1.0 per 100,000 children aged less than 15 years; 2) increasing to 80% in all provinces the percentage of AFP patients with two stool specimens within 0-14 days of onset of paralysis; 3) intensifying surveillance and supplemental vaccination in areas that might have circulating wild poliovirus (i.e., Guizhou province and Kashgar prefecture); 4) using a more specific surveillance case definition based on virologic confirmation of AFP cases (a strategy already being implemented in China); and 5) preventing reimportation of wild poliovirus into China from other neighboring polio-endemic countries. The second annual NIDs are scheduled for December 5 and 6, 1994, and January 5 and 6, 1995.

The successful eradication of wild poliovirus in the Americas and the experience in China suggest that a rapid reduction of wild poliovirus circulation can occur in virtually any geographic area if appropriate strategies and sufficient efforts are applied (3). The progress toward polio eradication in China indicates that the goal of eradicating wild poliovirus from the Western Pacific Region can be achieved.

References

1. CDC. National Poliomyelitis Immunization Days -- People's Republic of China, 1993. MMWR 1993;42:837-9.

2. Hull HF, Ward NA, Hull BP, Milstien JB, de Quadros C. Paralytic poliomyelitis: seasoned strategies, disappearing disease. Lancet 1994;343:1331-7.

3. CDC. Certification of poliomyelitis eradication -- the Americas, 1994. MMWR 1994;43:720-2.

* Mass campaigns over a short period (days to weeks) in which two doses of OPV are administered to all children in the target age group, regardless of prior vaccination history, with an interval of 4-6 weeks between doses. 

** A confirmed case of polio is defined as AFP and at least one of the following: 1) laboratory-confirmed wild poliovirus infection, 2) residual paralysis at 60 days, 3) death, or 4) no follow-up investigation at 60 days. The data reported from China are from the national AFP reporting system (provisional data through October 12, 1994).

Figure_1


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