Progress Toward Poliomyelitis Eradication --- India, 2002

Since the World Health Assembly resolved in May 1988 to eradicate poliomyelitis, the estimated global incidence of polio has decreased >99%, and three World Health Organization (WHO) regions (Americas, Western Pacific, and European) have been certified as polio-free (1). In 1995, India began accelerating polio eradication activities (2--4). By 2001, poliovirus circulation had been limited largely to the two northern states of Uttar Pradesh (UP) and Bihar, with 268 cases reported nationwide. However, in 2002, a major regional resurgence of polio occurred. As of January 25, 2003, a total of 1,556 cases were detected nationwide, of which 1,337 (86%) were in UP and Bihar. This report summarizes the status of polio eradication activities in India during 2002, analyzes the factors contributing to the resurgence, and describes the actions being taken to reduce poliovirus transmission.

Acute Flaccid Paralysis Surveillance

Acute flaccid paralysis (AFP) surveillance in India is facilitated by 203 trained surveillance medical officers who assist local health authorities in defined areas. Since 2000, India has exceeded the WHO-established AFP surveillance quality targets (i.e., a nonpolio AFP rate >1 per 100,000 population aged <15 years and adequate stool specimens* taken from >80% of persons with AFP) (Table). However, during 2002, nonpolio AFP rates were <1 per 100,000 population in five small states (Andaman and Nicobar islands, Arunachal Pradesh, Manipur, Nagaland, and Sikkim), and stool specimen collection rates were inadequate (i.e., <80%) in seven states (Andaman and Nicobar islands, Arunachal Pradesh, Bihar, Chhattisgarh, Delhi, Rajasthan, and UP). The nonpolio enterovirus isolation rate (target: >10%), a marker of laboratory performance and the ability to keep stool specimens refrigerated or frozen from collection to arrival at the laboratory, ranged from 11% to 26% in all nine polio laboratories in the national network.

Wild Poliovirus Incidence

During 2002, a total of 1,556 wild poliovirus cases were reported in India, a substantial increase from the 268 cases reported in 2001 (Table). Of these 1,556 cases, 1,445 (93%) were wild poliovirus type 1 (P1), 108 (7%) were wild poliovirus type 3 (P3), and three (<1%) were mixtures of P1 and P3. UP accounted for 1,218 (79%) cases, with 119 (7%) in Bihar and the remainder in other states. Cases were reported from a total of 155 (27%) of 584 districts nationwide, compared with 63 (11%) districts in 2001 (Figure 1). Wild poliovirus was detected in 65 (96%) of 68 districts in UP and in 29 (78%) of 37 districts in Bihar. P3 circulation was confined mostly to western UP, and the majority of cases occurring in eastern and central UP and in other states were P1.

During 2001--2002, the number of circulating major genetic lineages of wild poliovirus remained constant for P1 (n = three) and for P3 (n = four). Further analysis demonstrated that all lineages circulating in India during 2002 were derived from strains that circulated in UP during 2000--2001.

Vaccination Coverage

During 2001, approximately 70% of infants aged <1 year received >3 doses of oral poliovirus vaccine (OPV) through routine nationwide vaccination (Ministry of Health and Family Welfare, unpublished data, 2002). Substantial variations were found in routine coverage with 3 doses of OPV by state, ranging from 21% in Bihar to 97% in Kerala; routine coverage in UP was estimated to be 41% (United Nations Children's Fund [UNICEF], unpublished data, 2001).

Since 1995, biannual national immunization days (NIDs)^† that use fixed vaccination posts to administer OPV have been conducted to supplement routine vaccination. During 1999, supplementary immunization activities (SIAs) were intensified with the addition of house-to-house vaccination following an initial day of fixed-site activities. Two NIDs were conducted during December 2001 and January 2002, covering approximately 156 million and 163 million children aged <5 years, respectively. In addition, during September and November 2002, subnational immunization days (SNIDs)^§ were implemented in UP, Bihar, Delhi, and Haryana and in selected areas of West Bengal, Jharkhand, Gujarat, Madhya Pradesh, and Maharashtra, covering approximately 61 million and 60 million children aged <5 years, respectively. The number of large- scale NIDs/SNIDs conducted in India decreased from six during the 1999--2000 low poliovirus transmission season (winter months) to four during the 2000--2001 low season and three during the 2001--2002 low season (Figure 2).

During 2002, a total of 62 mop-up vaccination campaigns were conducted in specific areas in response to the detection of wild poliovirus, covering approximately 38 million children aged <5 years. During March and April 2002, two additional large rounds of house-to-house vaccination were conducted in high-risk areas of three states, covering approximately 8 million and 9 million children aged <5 years, respectively.

Vaccination coverage data from AFP cases that were not caused by poliovirus suggest a deterioration in OPV coverage in the general population of the majority of states with increased polio incidence in 2002, particularly in UP. In western UP, the proportion of patients aged <5 years with nonpolio AFP who had <3 OPV doses (routine or supplemental) was 13% in 2000 and 10% in 2001, but increased to 19% in 2002. In eastern and central UP, the proportion of nonpolio AFP patients aged <5 years with <3 OPV doses increased from 9% in 2001 to 33% in 2002.

Reported by: Ministry of Health and Family Welfare; National Polio Surveillance Project; Vaccines and Biologicals Dept, World Health Organization, Regional Office for South-East Asia, New Delhi, India. Vaccines and Biologicals Dept, World Health Organization, Geneva, Switzerland. Div of Viral and Rickettsial Diseases, National Center for Infectious Diseases; Global Immunization Div, National Immunization Program, CDC.

Editorial Note:

India, the only remaining country in the South-East Asia Region with ongoing indigenous wild poliovirus transmission, reported a major resurgence of polio in 2002. Surveillance data indicate that UP is the primary area in India with continuing poliovirus transmission. The main reason for continued transmission is insufficient OPV coverage through routine vaccination and SIAs.

The decline in OPV coverage in critical areas during 2002 had at least four primary causes. First, during 1999--2002, the number of NIDs/SNIDs decreased. Second, no NIDs or SNIDs were conducted during January--September 2002, an interval that permitted the accumulation of a large susceptible cohort of newborns. Third, the geographic extent of SIA implementation decreased. Although some smaller-scale SIAs ("responsive mopping-up" activities) were conducted in selected districts where cases occurred during early 2002, the majority of districts in eastern and central UP were not targeted, leaving this area at high risk. Finally, a substantial number of children were missed during SIA rounds. SIA monitoring data in western UP during June--August 2002 indicated that house-to-house teams failed to vaccinate children in <15% of houses in some districts. This suggests that hundreds of thousands of children were missed in areas where high population density, a very large birth cohort, and poor sanitation favor poliovirus transmission. One major factor contributing to poor SIA quality in UP was inadequate engagement and involvement of the general community, particularly members of minority groups.

Additional SIAs are planned for 2003, and major steps to improve SIA quality are underway. During January and February 2003, India had two NID rounds, targeting 164 million children in each. Four SNID rounds are planned in April, June, September, and November, targeting approximately 95 million children in four high-risk northern states (i.e., UP, Bihar, Haryana, and Delhi). These SNID rounds will be followed by two NID rounds in January and February 2004. Monitoring of SIA quality is being enhanced through new vaccinator data collection forms and standardized independent observer checklists that identify general programmatic areas of weakness and specific districts and blocks that show deficiencies in SIA quality. AFP surveillance reviews are being planned. Finally, the state government, WHO, and UNICEF are providing increased support through additional personnel and funding.

The 2002 outbreak in India represented a setback for the national and global polio initiative. However, appropriate steps are being taken to improve monitoring and SIA quality and to correct identified problems. In addition, the natural immunity from the outbreak will provide an opportunity to maximize the impact of SIAs in 2003. Finally, the outbreak alerted health authorities to the importance of avoiding complacency. To eradicate polio in India, national and state governments and major international partners must work together effectively. Conducting high-quality SIAs in a timely manner is essential in the final phase of the polio eradication campaign.

References

1. CDC. Progress toward global eradication of poliomyelitis, 2001. MMWR 2002;51:253--6.
2. CDC. Progress toward poliomyelitis eradication---India, 1998. MMWR 1998;47:778--81.
3. CDC. Progress toward poliomyelitis eradication---South-East Asia, January 2000--June 2001. MMWR 2001;50:738--42,751.
4. CDC. Progress toward poliomyelitis eradication---India, Bangladesh, and Nepal, January 2001--June 2002. MMWR 2002;51:831--3.

*Two specimens collected >24 hours apart within 14 days of paralysis onset and shipped properly to the laboratory.
^†Nationwide mass campaigns during a short period (days to weeks) in which 2 doses of OPV are administered to all children (usually aged <5 years), regardless of previous vaccination history, with an interval of 4--6 weeks between doses.
^§ Mass campaigns same as NIDs but limited to parts of a country.

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