An overview article in Nature Medicine, March 11, 2026, focuses on the clinical development of cancer vaccines. It highlights findings from recent clinical trials of cancer vaccines. Discusses critical factors for optimizing these vaccines. It focuses on proxies for vaccine effectiveness, which are measurable indicators of their effectiveness. It covers the selection of neoantigens, that is, specific tumor antigens to target the immune system. Describes modular platforms for vaccine development. It emphasizes the importance of early intervention in the treatment of cancer with vaccines.