Adamu Yusif, a 15-year-old victim of polio, along with classmates at his school. Despite all of the
progress made against polio, highly populated countries such as Nigeria continue to pose challenges to full immunization. More than 40 percent of Nigerians are under the age of 15 and extremely vulnerable to polio. The city of Kano has undertaken a campaign
to immunize more than 6 million children under the age of five. (Kano, Nigeria, 2010)
