Nature, Published online: 18 February 2026; doi:10.1038/d41586-026-00477-0

In an experimental trial, a personalized mRNA vaccine was tested in 14 individuals with an aggressive form of breast cancer. It trained immune cells to target cancer-specific mutant proteins, inducing strong, lasting immunity. Ten participants remained disease-free. Analysis of relapses revealed resistance mechanisms, offering essential insights for future therapies.