In early August, Israel launched a mass campaign to vaccinate children against polio, including this little girl at a clinic in Rahat. David Buimovitch/AFP/Getty Images hide caption

itoggle caption David Buimovitch/AFP/Getty Images

Ali Maow Maalin said he avoided getting the smallpox vaccine as a young man because he was afraid of needles. He didn't want others to make the same mistake with polio. Courtesy of the World Health Organization hide caption

itoggle caption Courtesy of the World Health Organization

A Yemeni child receives a polio vaccine in the capital city of Sanaa. The Yemen government launched an immunization campaign last month in response to the polio outbreak in neighboring Somalia. Mohammed Huwais/AFP/Getty Images hide caption

itoggle caption Mohammed Huwais/AFP/Getty Images

Health workers vaccinate a boy against polio at a May immunization drive in Mogadishu, Somalia. Farah Abdi Warsameh/AP hide caption

itoggle caption Farah Abdi Warsameh/AP

A baby receives a polio vaccine at the Medina Maternal Child Health center in Mogadishu, Somalia. The country has one of the lowest immunization rates in the world. Ben Curtis/AP hide caption

itoggle caption Ben Curtis/AP

There's no better deal than getting polio cases down to zero, philanthropist Bill Gates says. Marie McGrory/NPR hide caption

itoggle caption Marie McGrory/NPR

A baby receives a polio vaccine at the Medina Maternal Child Health center in Mogadishu, Somalia, on Wednesday. Somalia has one of the lowest immunization rates in the world. Ben Curtis/AP hide caption

itoggle caption Ben Curtis/AP

A child is immunized against polio at the health clinic in a farming village in northern Nigeria. The procedure involves pinching two drops of the vaccine into the child's mouth. For full protection, the child needs three doses, spaced out over time. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

A Nigerian health commissioner Dr. Sani Malam vaccinates a child for polio during a national immunization drive in Bauchi, Nigeria, last week. Deji Yake/EPA /Landov hide caption

itoggle caption Deji Yake/EPA /Landov

A child is inoculated with the polio vaccine at a traffic checkpoint just outside Pakistan's capital, Islamabad. Roadside vaccinations help health workers reach children in mobile populations. Jackie Northam/NPR hide caption

itoggle caption Jackie Northam/NPR

A health worker in Pakistan marks a child's finger with ink after giving him the polio vaccine. Jackie Northam/NPR hide caption

itoggle caption Jackie Northam/NPR

Ado Ibrahim carries his son Aminu through a village in northern Nigeria. Aminu, 4, was paralyzed by polio in August. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

Health workers transport the polio vaccine by donkey in southeastern Pakistan. Asad Zaidi/Courtesy of UNICEF Pakistan. hide caption

itoggle caption Asad Zaidi/Courtesy of UNICEF Pakistan.

An Indian child receives the oral polio vaccine. Twice a year, an army of 2 million volunteers fans out across India to administer the vaccine. India has not reported a single case of polio in more than a year-and-a-half. Julie McCarthy/NPR hide caption

itoggle caption Julie McCarthy/NPR