A bare gene (strand of DNA) that has been extracted from or derived (e.g., synthesized from sequencing data) from a pathogen. During the 1990s, it was discovered that inserting such “naked” genes into certain tissues in the (usual disease host) organism would sometimes cause those tissues to take up the “naked” genes and express some of the cell-surface proteins indigenous to that pathogen. When that happens, and the (host’s) immune system mounts an immune response (to those cell-surface proteins, and thus to the pathogen), these “naked” genes are referred to as “DNA vaccines.”