Polio's Last Stand?

Part of the problem is biological. Since most people who have polio do not show signs of infection, outbreaks are hard to control. With diseases where there are symptoms, for example smallpox, health officials can vaccinate people who have been in close contact with a patient. According to Bill Moss, a pediatrician at Johns Hopkins, the same strategy doesn’t work for polio. If 95 percent of those infected with polio are outwardly healthy, how do you determine who should be vaccinated? “You’re only seeing the tip of the iceberg,” he says.

Instead, health workers try to immunize all children, giving special attention to communities where outbreaks occur. But the strategy presents logistical challenges. Transporting the oral vaccine - which must be refrigerated - to every child under the age of five in remote and roadless corners of the developing world is a daunting task. Inevitably, some children never receive it.

In Nigeria, 28 percent of the children in the hardest hit areas have not received a single dose of the vaccine. But even those who are vaccinated are not necessarily protected. “The correlation between vaccination and immunity is not one to one,” says Moss. While three doses of the oral polio vaccine leads to immunity in almost everybody, a single dose only provides full protection in about half the recipients.

Another difficulty is what Moss calls “community fatigue.” Health workers go to rural villages several times a year. Parents get tired of bringing their children—many of whom have already been vaccinated—to get another shot to protect them from a relatively rare disease. Many villagers question why the government is not addressing more prevalent health concerns, such as diarrhea in children. In order to have a successful eradication campaign, participation is obligatory. “A country can’t say, polio is a problem, but our kids are dying of pneumonia and diarrhea and we want to put our resources there,” says Moss. “In some places, they’re not even answering the door anymore when the vaccinators show up.”