Efforts to develop peptide-based vaccines, in particular those requiring site-specific targeting of self-proteins, rely on the ability to optimize the immunogenicity of the peptide epitopes. Currently, screening of candidate vaccines is typically performed through low-throughput, high-cost animal trials. To improve on this we present the program EpIC, which enables high-throughput prediction of peptide immunogenicity based on the endogenous occurrence of B-cell epitopes within native protein sequences. This information informs rational selection of immunogenicity-optimized epitopes for peptide vaccines.