Figure 1. Immunochemically dynamic vaccine. The heroin molecule itself is too small to elicit an immune response. Thus, a team from The Scripps Research Institute attached the molecule to a carrier protein to provide a sufficiently large antigenic entity to present to the immune system. Typically vaccines lead to production of antibodies that target one antigen. Initially, the Scripps vaccine works the same way, with the heroin-like vaccine leading to production of antiheroin antibodies. However, the body slowly metabolizes the vaccine, resulting in 6-acetylmorphine-like and morphine-like vaccines. This leads to production of antibodies targeting those two psychotropic metabolites, demonstrating the vaccine's dynamic aspect. (Figure based on Figure 1 in ref. 1.)