The Associated Press examines how the oral polio vaccine, “made from a live polio virus — albeit weakened,” is contributing to the spread of the disease in Nigeria. While vaccinated children can pass the virus on to non-immunized children through waste in the water supply, which gives them some protection against polio, “in rare instances, as the virus passes through unimmunized children, it can mutate into a strain dangerous enough to ignite new outbreaks, particularly if immunization rates in the rest of the population are low,” according to the news service. Even though vaccination coverage rates in Nigeria have improved, officials say about 95 percent of the population needs to be vaccinated to attain eradication.

In 2007, health experts said that 69 children had been paralyzed in a new outbreak that was the result of a vaccine virus mutation. “WHO said the vaccine-linked outbreak would be swiftly overcome — yet two years later, cases continue to mount,” according to the news service. This year in Nigeria, “the number of polio cases caused by the vaccine has doubled: 124 children have so far been paralyzed, compared to 62 in 2008, out of about 42 million children vaccinated. For every case of paralysis, there are hundreds of other children who don’t develop symptoms, but pass on the disease,” the AP reports.

“Nigeria’s vaccine-linked outbreak underlines the need to stop using the oral polio vaccine as soon as possible, since it can create the very epidemics it was designed to stop, experts say,” the AP writes. Developing countries use the oral vaccine, because “it’s cheaper, easier, and protects entire communities” rather than the vaccine used in developed countries, which does not contain the live virus, the AP reports. “Until a better vaccine is ready, WHO and U.S. CDC officials say the oral vaccine is the best available tool to eradicate polio and that when inoculation rates are nearly 100 percent it works fine,” according to the AP (Cheng, 8/14).

Nature’s blog, the “Great Beyond,” writes that the spread of polio because of a vaccine mutation “is particularly meaningful in Nigeria, which has had a prickly relationship with polio eradication campaigns.” According to the blog, switching from live vaccines to injected vaccines might not be the “perfect answer” because live vaccines are “thought to be better for regions where the disease is still endemic” (Buchen, 8/14).