Polio eradication efforts lost ground in 2008

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Apr 2, 2009 (CIDRAP News) – The world lost some ground last year in its 20-year push to eradicate polio, mainly because the disease has spread to new parts of Nigeria and because conflict in Afghanistan and Pakistan have made it difficult to get vaccines to children, the US Centers for Disease Control and Prevention (CDC) reported today.

Though the incidence of polio has decreased drastically since 1988 when the Global Polio Eradication Initiative (GPEI) was established, polio cases increased 26% in 2008—to 1,655, up from 1,315 cases in 2007, according to a report in the Apr 3 issue of Morbidity and Mortality Weekly Report (MMWR).

Much of the increase stemmed from a spike in cases in Nigeria, which rose from 285 cases in 2007 to 801 cases in 2008. The authors noted that wild poliovirus type 1 (WPV1) spread last year from endemic areas in northern Nigeria to polio-free southern states and eight neighboring countries, six of which had been polio-free since the 2003-to-2005 timeframe. The increase was also coupled with suboptimal vaccine coverage for children in Nigeria's high-risk northern states.

Also, India saw its 3-year handle on WPV1 transmission in western Uttar Pradesh state erode when the virus entered the state from neighboring Bihar state in mid 2008.

In Afghanistan and Pakistan in 2008, vaccination efforts in children were met by increases in WPV1 and wild polio type 3 (WPV3) cases, the CDC authors reported. Even in more secure areas of Pakistan, management and operational problems hampered vaccination efforts.

Most vaccination efforts in developing countries involve a less expensive vaccine that contains live, attenuated virus that multiplies in the gut, providing passive immunization to other people. However, the vaccine virus sometimes mutates into a virulent type that can cause polio paralysis and spread through shedding to those who aren't vaccinated.

In 2008, vaccine-derived polioviruses were detected in patients with acute flaccid paralysis from eight countries.

The global vaccination rate of infants with three doses of the trivalent oral polio vaccine (OPV3) for 2007, the most recent year data were available, was estimated at 82%. For the countries in which the wild poliovirus is endemic, vaccination rates were 83% in Afghanistan and Pakistan, 62% in India, and 61% in Nigeria. However, the authors pointed out that OPV3 coverage in some parts of the countries dipped below 40%.

In an editorial note that accompanied the polio trend report, the authors said that two World Health Organization (WHO) advisory bodies acknowledged the eradication obstacles and concluded that to drive the number of cases downward again, public health officials need to win the vaccination outreach and coverage cooperation of all affected countries and enhance routine vaccination and surveillance efforts.

The groups noted some promising development in the affected countries, including the interruption of indigenous WPV1 transmission in India's Uttar Pradesh state and new management approaches with intensive immunization activities in Nigeria, Pakistan, and Afghanistan.

They singled out an especially challenging situation in India, where OPV effectiveness is low, purportedly due to the combination of diarrheal diseases, malnutrition, and crowding.

Last summer, GPEI members, which include the WHO, the CDC, UNICEF, and Rotary International, declared a "final push" toward eradicating polio and launched a 3-year $100-million fund drive toward easing some of the shortfall in eradication efforts. The WHO has estimated the funding gap to be $490 million beyond what governments and other organizations have promised.

CDC. Progress toward interruption of wild poliovirus transmission—worldwide, 2008. MMWR 2009 Apr 3;58(12):308-12 [Full text]

See also:

Oct 16, 2008, CIDRAP News story "Polio vaccination may continue after wild virus fades"

Jun 18, 2008, CIDRAP News story "Coalition declares 'final push' to end polio"

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