Polio is spreading in Nigeria and health officials say in some cases it’s caused by the vaccine used to fight the paralyzing disease.
In July, the World Health Organization issued a warning that this particular virus might extend beyond Africa. So far, 124 Nigerian children have been paralyzed this year — about twice those afflicted in 2008.
Nigeria and most other poor nations use an oral polio vaccine because it’s cheaper, easier, and protects entire communities. But it’s made from a live polio virus which carries a small risk of causing polio. In even rarer instances, the virus in the vaccine can mutate into a deadlier version that ignites new outbreaks.
[Source]
Chapter: Vaccines :: 3 December 2009
