An off-the-shelf neoantigen priming vaccine comprised of a great ape adenovirus (GAd) encoding tumor-specific neoantigens (TSNAs) derived from as of yet undisclosed frameshift peptides (FSPs) with potential immunostimulatory and antineoplastic activities. Upon intramuscular administration of the adenoviral tumor-specific neoantigen priming vaccine GAd-209-FSP, the adenovirus infects cells and expresses the TSNAs. This stimulates the host immune system to mount a cytotoxic T-lymphocyte (CTL) response against tumor cells expressing the TSNAs, leading to tumor cell lysis. Adenoviral-TSNA priming vaccine GAd-209-FSP is followed by boosting with a vaccine that encodes the same target TSNAs.