 From VOA Learning English, this is the health report. Most countries are now free of polio, but the disease remains a threat in some countries, including Nigeria. Gregory Hussie is the director of the Vaccines for Africa initiative at the University of Cape Town in South Africa. He says there is a worldwide movement to eradicate polio in the next five to ten years. He says there are problems in Nigeria because people are refusing to immunize their children for a number of reasons. The World Health Organization says after polio vaccination campaigns were interfered with in northern Nigeria several years ago, the virus there spread all the way to Ethiopia. Gregory Hussie says continued outbreaks of measles represent another failure. The United Nations and other international agencies have immunization campaigns, but Africa lacks its own major programs. The Vaccines for Africa initiative was started to spread knowledge about vaccines not only to health care workers, but to policymakers and communities. But Gregory Hussie says cost remains a major problem. An international public-private partnership, the GAVI Alliance, helps developing countries offer vaccines. GAVI negotiates with drug companies to lower the cost of medicines. But Gregory Hussie warns that low-cost vaccines will not be available forever. He says some countries that have enough money to vaccinate children have not made that a top goal. Researchers at the University of Cape Town say African leaders must be held accountable for meeting immunization targets and honoring international commitments. For VOA Learning English, I'm Laurel Bowman.