(Biological products biologicals) any virus, therapeutic serum, toxin, anti-toxin, or analogous product of plant or animal origin used in the prevention, diagnosis, or treatment of disease. Biologics, including vaccines and blood plasma products, are regulated by the Bureau of Biologics, a division of the Food and Drug Administration. They differ from drugs in that biologics are usually derived from living microorganisms and cannot be synthesized or readily standardized by chemical or physical means. They tend to be chemically less stable than drugs, their safety cannot be as easily assured and they are never as chemically pure as drugs.