ATLANTA - The World Health Organization (WHO) during 1999 stepped up efforts to eradicate polio worldwide by the end of 2000 by improving the number and quality of vaccination rounds administered. As a result, the number of polio-endemic countries decreased.
According to the Centers for Disease Control and Prevention (CDC), the number of known or suspected countries where polio is endemic decreased from 50 to 30 during 1998-1999. Type 2 poliovirus is now almost extinct; the only known remaining foci are in northern India. Additional chains of type 1 and type 3 polio transmission have been broken and virus sublineages have become extinct, according to the CDC.
During National Immunization Days (NIDs) and Subnational Immunization Days (SNIDs) in 1999, approximately 470 million children younger than 5 were vaccinated in 83 countries. The number of NID rounds in priority countries (those considered major global virus reservoirs or affected by conflict) increased.
House-to-house vaccination was used increasingly, both in high-risk areas during "intensified NIDs" and exclusively in large-scale SNIDs in Nigeria and Pakistan. In Nigeria, house-to-house SNIDs reached 20% to 40% more children (depending on the state) younger than 5 compared with the last fixed-post NID round.
Surveillance for acute flaccid paralysis (AFP) also improved in 1999. The number of cases reported from the African Region tripled, while average specimen collection rates were maintained or improved in four of the six WHO regions.
Despite the decrease in the number of countries where polio still circulates, from 1998 to 1999 the total number of reported polio cases increased 10%. However, the CDC said this reflects the improved AFP reporting from Africa and also a wild poliovirus type 3 outbreak in Angola. Cases reported in Africa rose from 993 in 1998 to 2,825 in 1999. Over the same period, cases reported in the Eastern Mediterranean Region increased from 555 to 814. However, polio cases reported from the South-East Asian Region declined from 4,775 in 1998 to 3,330 in 1999.
War, civil unrest and political instability made it impossible to reach all unvaccinated children in Angola, Congo Brazzaville, the Democratic Republic of Congo, Nigeria and Sierra Leone last year. However, according to the CDC, achieving immunization in conflict-affected areas is feasible, as demonstrated by the "days of tranquility" established for NIDs in the Democratic Republic of Congo in 1999 by the United Nations Secretary General and other partners.
In October and November 1999, NIDs were postponed in Burkina Faso, Chad, Ghana, Kenya, Niger, Sierra Leone and Togo because of a global shortfall in the oral polio vaccine supply.
Three WHO regions have surpassed or are approaching certification level standards. The Western Pacific Region will be certified this year.
For more information:
- CDC. Progress toward global poliomyelitis eradication, 1999. MMWR. 2000;49(16):349-354.
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