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.
1 A vaccine is a product that produces immunity from a disease and can be administered through needle injections, by mouth, or by aerosol.  A vaccination is the injection of a killed or weakened organism that produces immunity in the body against that organism.