Abstract
BACKGROUND: The USA has traditionally been the largest donor to health programmes in low-income and middle-income countries (LMICs). In January 2025, almost all such funding was stopped and prospects for its resumption are uncertain. The suddenness of the funding cuts makes it difficult for national health programmes in LMICs to adapt. We aimed to estimate the impact of these cuts on deaths and other outcomes (new infections, number of family planning users, and unplanned pregnancies) for four health areas that have been a focus of a substantial amount of US foreign assistance: HIV, tuberculosis, family planning, and maternal and child health. METHODS: We applied established mathematical models to the countries receiving US foreign assistance in each domain to estimate health impacts over the period 2025 to 2030. We used six models of HIV, three different approaches to estimate family planning impact, and one model each for tuberculosis and maternal and child health, applying these models to as many as 80 countries. We compared model projections assuming constant funding (status quo) with projections assuming complete elimination of US funding in each country. Some models also considered partial cuts or restoration of funding over time. FINDINGS: A complete cessation of US funding without replacement by other sources would lead to drastic increases in deaths from 2025 to 2030: 4·1 million (range 1·6-6·6) additional AIDS-related deaths across 55 countries, 606 900 (95% uncertainty interval [UI] 466 000-768 800) additional tuberculosis deaths across 79 countries, 40-55 million additional unplanned pregnancies and 12-16 million unsafe abortions across 51 countries, and 2·5 million (1·3-4·5) additional child deaths from causes other than HIV and tuberculosis across 24 countries. Restoration of funding for HIV treatment but not prevention would avoid most of the increase in deaths but still result in nearly 1 million more new HIV infections from 2025 to 2030. INTERPRETATION: Substantial progress has been made in improving global health in the past few decades. This progress has strengthened hope in reaching global development goals. However, the recent funding cuts threaten to change these trajectories and could lead to sharp increases in avoidable mortality for the poorest countries. Even a partial restoration of US funding would combat the most severe effects and provide time for countries that have received substantial US foreign assistance to adjust to the new funding landscape. FUNDING: Economic and Social Research Council; Engineering and Physical Sciences Research Council; European and Developing Countries Clinical Trials Partnership; Gates Foundation; Global Fund to Fight AIDS, Tuberculosis, and Malaria; Open Philanthropy; UK Foreign, Commonwealth & Development Office; UK Medical Research Council; UN Population Fund; UNAIDS; US National Institute of Allergy and Infectious Diseases; University of Edinburgh; US National Institutes of Health; US President's Emergency Plan for AIDS Relief; Wellcome Trust; World Bank; WHO.