Five‑year follow‑up data show adding Merck & Co. and Moderna’s cancer vaccine candidate to Keytruda delivered a sustained 49% reduction in the risk of recurrence or death in melanoma patients. The update reports continued durable benefit across the extended follow‑up window. The result strengthens the case for mRNA‑based cancer vaccine strategies combined with checkpoint inhibition and feeds into development plans as companies advance toward larger, registrational studies. Sponsors and investors will watch regulatory and phase‑3 planning closely; sustained long‑term benefit is a critical endpoint for adjuvant oncology vaccines.