Nature, Published online: 19 February 2025; doi:10.1038/d41586-025-00470-zCancer vaccines must induce immune cells, called CD8+ T cells, that can recognize cancer cells over the long term. In pancreatic cancer, a common and deadly cancer, RNA vaccines that encode neoantigens mutant proteins found only in cancer cells induce substantial numbers of long-lived CD8+ T cells with preserved function, and their presence correlates with better clinical outcomes at a three-year follow-up.