AlQa'dah 20, 1436, Sep 4, 2015, SPA -- The U.N. Children's Fund (UNICEF) and the World Health Organization (WHO) called Friday on parents in Ukraine to vaccinate their children following a confirmed polio outbreak in the country. "The only effective way to protect children from polio is vaccination," UNICEF Ukraine representative Giovanna Barberis said in a statement. "The available vaccines supplied by UNICEF should be used as soon as possible to ensure children are protected from polio in Ukraine." Similarly, WHO Ukraine chief Dorit Nitzan said, "WHO recommends large-scale immunization activity. ... [The vaccine] is safe and effective and ready to be distributed and used." Aid organizations face major challenges in getting access to the most vulnerable of an estimated 5 million people affected by conflict in eastern Ukraine.