Pakistan remains a hotbed for polio, years after the rest of the world (aside from Afghanistan) completely eradicated the disease. The country continues to have a high number of polio cases due to barriers preventing vaccination efforts, primarily violence against health workers and a hesitance among locals to trust a Western excursion of immunization.

According to the World Health Organizaion (WHO), polio cases have decreased by 99 percent since 1988 thanks to widespread immunization efforts. However, that doesn’t mean the world is completely free of worry. “[A]s long as a single child remains infected with poliovirus, children in all countries are at risk of contracting the disease,” WHO notes. “The poliovirus can easily be imported into a polio-free country and can spread rapidly among unimmunized populations.”

In a new VICE video, the narrator notes that a fraction of parents in Pakistan are often wary or fearful of having their children vaccinated, concerned that immunization is a “foreign plot to harm Muslims.” Health workers and Pakistani officials have attempted to combat community opposition through awareness campaigns, but at times they’ve even had to resort to arresting parents for refusing to vaccinate their kids. In 2015, 471 parents were arrested for denying polio vaccinations.

In addition to cultural barriers, violence is still possibly the biggest deterrent of immunization campaigns. Attacks carried out by the Taliban have targeted polio workers since 2012, killing hundreds of people. As a result of these obstacles, Pakistan had the most new cases of polio last year, while Afghanistan has nearly succeeded in eradicating the virus.

In the hopes of improving vaccination rates in Pakistan and Afghanistan, WHO recently undertook a switch of vaccine shots — from one that protects against type 1, type 2, and type 3 polio to a bivalent one that targets only types 1 and 3. They chose to switch because polio type 2 transmission has been eradicated since 1999, and it’s possible that a weakened type 2 virus in the blood may cause vaccine-derived infections. Health officials hope the switch will aid in Pakistan’s fight against polio.