Special challenges have become apparent in three nations where polio remains endemic: Pakistan, Nigeria and Afghanistan. But in Pakistan, a renewed effort to tackle misperceptions about the vaccine appears to be working, say experts speaking this week at the annual meeting of the American Society of Tropical Medicine and Hygiene.
Worldwide, there were 177 polio cases through October of this year, a drop from 502 during the same period last year. In Pakistan, cases fell from 198 in 2011 to 56 so far this year. International public health leaders hope that polio will become the second human disease, after smallpox, to be completely eradicated.
"There is a lot of evidence of progress," Dr. Steven Wassilak, a medical epidemiologist and polio expert at the Centers for Disease Control and Prevention, told Take Part. "The ultimate progress we want to see is zero cases in each of these countries that have not stopped polio outbreaks. It doesn't matter until you get to zero in those three countries."
Wassilak presented a study this week showing that of the two types of wild polio virus, WPV1 and WPV3, circulating in Pakistan, the one known as WPV3—or type 3—is close to being eliminated. There have been no outbreaks of type 3 cases in six months, the longest disease-free period to date.
"It seems to be approaching its last gasp of breath," he says.
CDC is one of four organizations leading the Global Polio Eradication Initiative. Other partners include Rotary International, UNICEF and the World Health Organization, with support from the Bill and Melinda Gates Foundation. In September, leaders of the initiative met to voice support for the polio Emergency Action Plan, which is a "surge of human resources" involving 4,000 people who have been deployed to complete the eradication effort.
Those resources are needed in Pakistan, Dr. Anita Zaidi, a pediatrician at Aga Khan University University in Karachi, who serves on Pakistan's National Immunization Technical Advisory Group, told Take Part. After an intense effort to track down unimmunized people and offer free vaccine, health leaders in Pakistan now say the problem is only partly one of access. Too many people flat-out refuse the vaccine, she says.
In a recent study on immunization efforts in Karachi, Zaidi found parent refusal accounted for 74 percent of missed immunization opportunities. Karachi is the only city in the world that has not stamped out polio transmission, mostly due to persistent myths about vaccination, she says.
"Pakistan is putting in a lot of effort, but there are some individuals that are persistently missed," she says. "They are missed because they are not reached —which used to be the case—or they are reached but they refuse to take the vaccine."
The vaccination effort has been hampered by false rumors circulating in some communities that immunizations cause sterility or contaminated with HIV. Vaccine resistance is especially strong in the Pashtun population .
"We've also found through our work that these ideas are actively promulgated in the community," Zaidi says. "There is propaganda against a program that is seen coming from Western nations"
Especially troubling are recent events in Karachi that suggest a type of anti-vaccine uprising. A health worker involved in the polio campaign was killed recently and the child of another worker was kidnapped but later safely returned. Zaidi said that she recently participated in a polio seminar in Karachi where concerns about violence prompted the organizers to avoid any publicity
Nevertheless, the effort to educate people about the vaccine continues with a fresh strategy of relying on community elders and leaders to support the program, she says.
"To counter those beliefs one has to be at the grassroots level of the communities and use trusted community elders and leaders to discuss the value of the vaccine," Zaidi says. The engagement of community leaders and elders is now underway.
"I think that we will probably not reach eradication targets in 2013, but I think they're reachable," Zaidi notes. "I think we'll get the job in the next year or two. It's really about building trust with this community and educating people."
Elsewhere in Pakistan, reaching eradication simple means finding hard-to-reach people who move around the country due to conflicts in the north and along the Afghanistan border. That's a significant challenge, she says. For every confirmed cases of polio there are another 200 asymptomatic carriers of the virus.
"The greatest challenges are in areas of open, active conflict," says Olen Kew, senior scientific advisor with the division of viral diseases at CDC. "There is what we call a corridor of migration and polio transmission."
Similar tactics are also needed in Nigeria, where the number of polio cases has risen for the second straight year. According to another presentation at the meeting, by Dr. Adamu Nuhu, of Nigeria's National Primary Healthcare Development Agency, cases are confined to the northern part of the country, where opposition to immunizations is rooted in religious or political differences and in rumors of vaccine-induced sterilization and HIV infection.
But eradicating polio in Nigeria is also essential to prevent outbreaks in Sudan, Chad and other nearby countries.
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