While U.S. policymakers struggle with efforts to stymie the resurgence of measles globally—in recent months cropping up at seemingly innocuous places like Disneyland—countries are faced with a beast of a different nature. In the United States, we are fortunate to be armed with a large supply of vaccines that have all but eliminated the most frequent killers of children under the age of 5, including smallpox, tetanus, and measles. In the developing world, however, there’s still a long way to go.