Islamic extremists made Imana Alhaji Gana's village in northeastern Nigeria too dangerous for health workers to vaccinate against polio. Now that she and her family have fled to a displacement camp, those workers want to catch her children in time.Here in the camps housing thousands of families seeking safety from the extremists, health teams are going from tent to tent, inoculating youngsters against the disease that withers limbs and disables children for life.At first, Gana is afraid to let the outreach workers vaccinate her baby. Eventually they persuade her that the three-week-old child is not too young for immunization, which can take place as early as the day of birth.The complicated fight against polio is yet another way the Nigeria-based extremist group Boko Haram has disrupted life in the northeast, leaving children vulnerable to an entirely preventable disease."When such children come to the camps or host communities they become a threat to other children," said Almai Some, the field coordinator in Borno state for the vaccination campaign run by Rotary.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and FacebookSome of the families arriving are from areas where polio vaccinators have not been able to visit for as long as six years.Boko Haram's insurgency began in Maiduguri, Borno state's capital, but its reach has expanded beyond Nigeria's borders to neighboring Niger, Chad and Cameroon. Its violence has proved to be a major setback to the international campaign against polio.Nigeria is one of just three countries where polio is endemic and has not been eliminated, along with Pakistan and Afghanistan. The final phase to wipe out polio is "proving to be extraordinarily difficult" because "the poliovirus is surviving despite all the good work and in the face of everything that is being thrown at it," said a WHO-appointed monitoring group at the end of last year.In Nigeria, there is little or no surveillance data in Borno state, and "unless there is a breakthrough to reach those areas in Borno, the entire polio (eradication) program is at risk," said the monitoring group. Nigeria had other outbreaks last year including cholera, hepatitis, monkeypox, Lassa and yellow fevers, showing the challenges to the country's health care system. Globally the campaign to eradicate polio has been faced with outbreaks last year in non-endemic countries like Congo and Syria.The World Health Organisation had declared Nigeria polio free in September 2015 after it went a year without any new cases. But in 2016 — after two years with no cases — fresh polio cases broke out in three locations in Borno state. No new cases were reported in Nigeria in 2017 or so far this year.Fearful of polio vaccination Now the WHO says it will be spending $127 million toward eradicating polio in Nigeria between 2018 and 2019. Rotary's program is helping that effort by targeting some 2.1 million children in 24 accessible local governments. But there are still three areas in Borno state that are not included because of ongoing instability: Kala-Balge, Marte and Abadam. For those unreachable areas, the vaccinators train Nigerian soldiers in how to administer the vaccines.In a few cases, villagers have reported being threatened by Boko Haram fighters to avoid the polio vaccine. And in 2013 a number of vaccinators were attacked and killed by the extremists, leading some of their colleagues to disguise their vaccine carriers or hide them under their hijabs.In addition to the threat posed by Boko Haram, some communities are still fearful of the polio vaccine after years of misinformation that it can cause sterility and other health problems."Many people now accept the vaccine against polio, but there are still more cases of rejections here and there and we are doing our best to tackle them," said Digma Zubairu, district head in Shehuri-North.Falmata Kolo, a 21-year-old volunteer with Rotary's outreach program Polio Plus, said she works to reassure people that the vaccinations are safe."I also tell them should your child contract polio and grew up to understand that his or her parent had a chance to prevent the disease but failed, the child would never forgive the parents," she said. "This kind of message actually spurs many mothers to offer their kids for the vaccine."Fatimah Muhammed, a 45-year-old mother of six, says parents should accept the vaccine."Today we have children that had taken the vaccine some 15 years ago who are married and are even having children of their own," she says. "So my advice for my fellow mothers who have kids under the age bracket (6 years old) to get them to take the vaccine because it is good."