How should we allocate international aid to improve healthcare in a fair and efficient way between countries? The UN Sustainable Development Goals to end the epidemics of communicable diseases and ensure universal access to healthcare have put this question high on the political agenda of global health. We propose a simple framework where we distinguish between allocation in the short and in the long run. In the short run, we show that individual access to healthcare measured by a newly derived healthcare poverty line, political will, and the epidemiological context of countries can explain differences in preventable health outcomes. A country’s financial means or gross national income (GNI) per capita does not affect its health outcomes in the short run. In the long run, however, we argue that countries can take appropriate measures to expand health coverage and improve healthcare systems, depending on their GNI per capita. Combining health outcomes and GNI per capita, we estimate a health development path that serves as the basis for our framework to allocate international aid. This framework also prescribes how long it takes for each country to move from the short to the long run.