Ukrainian deputy minister of health Igor Pereginets holds a 2-year-old getting a polio vaccination in Kiev on October 21 — part of a campaign launched after two cases were reported in September. Genya Savilov/AFP/Getty Images hide caption

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April 1959: Bottles containing the polio vaccine. M. McKeown/Getty Images hide caption

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The Oral Polio Vaccine Can Go 'Feral,' But WHO Vows to Tame It
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Two polio cases have been reported in Ukraine, where some parents are fearful of vaccinations. Above: A child receives the diphtheria, whooping cough and tetanus vaccine in a children's hospital in Kiev. Sergei Chuzavkov/AP hide caption

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These two Portuguese language posters are pro-inoculation. The one at left, produced in 1977, says, "Vaccinate and protect the children." The one at right, from '87, sends a similar message, noting that vaccination offers an opportunity for every youngster. National Library of Medicine hide caption

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A child is vaccinated in Makadara Health Clinic, Nairobi, Kenya. Greg Warner/NPR hide caption

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Catholic Bishops In Kenya Call For A Boycott Of Polio Vaccines
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At the health clinic in Minjibir, Nigeria, a child is immunized for polio. David Gilkey/NPR hide caption

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Polio Is Active In Only 3 Countries. Soon It Could Be Down To 2
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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

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Nigeria Is On The Verge Of Bidding Goodbye To Polio
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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

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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

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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

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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

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Helping Children, Despite Death Threats: A Vaccinator Explains
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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

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Polio's Surge In Pakistan: Are Parents Part Of The Problem?
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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

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The Hidden Costs Of Fighting Polio In Pakistan
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