Bid rent theory in the central business district (CBD) [edit]. Land users, whether they be retail, office, or residential, all compete for the most accessible land within the CBD. The amount they are willing to pay is called bid rent.
Recombinant or purified protein vaccines consist of protein antigens that have either been produced in a heterologous expression system (e.g., bacteria or yeast) or purified from large amounts of the pathogenic organism.
Attenuated vaccine. An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable (or live). Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by killing the virus (inactivated vaccine).