Vector-based and peptide vaccines

Both approaches serve the same purpose — showing the immune system a target found on cancer cells — but take different routes. A peptide vaccine contains short protein fragments copied from tumor-associated antigens, usually injected together with an adjuvant, a substance that heightens the immune system's attention. Antigen-presenting cells pick the fragments up and display them to T cells, which can then recognize tumor cells carrying the same antigen. A vector vaccine instead packs the genetic instructions for an antigen into a carrier — most often a weakened or engineered virus that cannot cause disease. Cells that take up the vector produce the antigen themselves, and the vector's natural ability to alarm the immune system can strengthen the response. Researchers are testing both classes across many tumor types, frequently in combination with checkpoint inhibitors, on the premise that the vaccine supplies the target while the second drug releases the immune response directed at it.