Personalized cancer vaccines aim to broaden the anti-tumor T cell repertoire by targeting neoantigens unique to each patient’s tumor, but immunogenicity has been inconsistent. In this issue of Cell, Blass, Keskin, Tu et al. evaluate NeoVaxMI, a multi-adjuvant personalized synthetic long-peptide vaccine administered with nivolumab in patients with melanoma. NeoVaxMI elicited stronger CD4+ and CD8+ responses than earlier iterations, and vaccine-induced T cells trafficked to regressing metastatic lesions.