The U.S. and Japan focused their cooperation on Africa. One example is joint funding that supported National Immunization Days in Zambia. The two countries worked together at a policy level as well as on the ground, coordinating U.S. Peace Corps and Japan Overseas Cooperation Volunteers. Polio now only occurs in less than five countries (thanks to initiatives like this and many others). Although not eradicated yet, by 2001 polio cases had been reduced by 99% since 1988.