At the health clinic in Minjibir, Nigeria, a child is immunized for polio. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

In this 2012 photograph, Adamu Ali carries his 4-year-old son, Omar, who was stricken with polio earlier that year. They live in the Nigerian village of Minjibir. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

A comic book captures the attention
 of Guinea worm patients Sadia Mesuna (right) and Fatawu Yakubu at a center for patients in Ghana. Louise Gubb/Courtesy of The Carter Center hide caption

itoggle caption Louise Gubb/Courtesy of The Carter Center

The documentary film, "Every Last Child," chronicles the efforts to eradicate polio in Pakistan. Women play a key role — they're welcome in homes to share information, while men are not. Courtesy of "Every Last Child" hide caption

itoggle caption Courtesy of "Every Last Child"

A child receives a polio vaccine during National Immunization Days in the Nigerian city of Kano. Diego Ibarra Sanchez /Courtesy of Rotary Foundation hide caption

itoggle caption Diego Ibarra Sanchez /Courtesy of Rotary Foundation

A health worker vaccinates a child during a polio campaign in Bannu, Pakistan, June 25. The Taliban threaten to kill vaccinators and parents who immunize their kids. A Majeed/AFP/Getty Images hide caption

itoggle caption A Majeed/AFP/Getty Images

Usman (right), 7 months, and Abdullah (left), 18 months, are held by their mothers while they wait to receive the polio vaccine at the Jalozai refugee camp near Peshawar, Pakistan. Daniel Berehulak/Getty Images hide caption

itoggle caption Daniel Berehulak/Getty Images

During nationwide polio campaigns, hundreds of thousands of health workers go door to door, giving children two drops of the polio vaccine. Anadolu Agency/Getty Images hide caption

itoggle caption Anadolu Agency/Getty Images

A health worker gives a child the polio vaccine in Bannu, Pakistan, June 25. More than a quarter-million children in Taliban-controlled areas are likely to miss their immunizations. A. Majeed/AFP/Getty Images hide caption

itoggle caption A. Majeed/AFP/Getty Images