A three-arm phase I clinical trial tests the safety (number of patients experiencing treatment-related AEs), efficacy (OS at 12 months), and immunogenicity of an H3.3K27M-specific short peptide vaccine, combined with the tetanus toxoid peptide and using Montanide and poly-ICLC as adjuvans, previously shown to elicit CD8-driven T cell responses in experimental models, in pediatric patients with newly diagnosed DMG or other glioma in combination with the ICI nivolumab in one arm (NCT 02,960,230) (see also the “Improving Vaccine Efficacy” section). Here, CD8A is linked to central nervous system cancer.