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randomized trial

a study in which participants are assigned by chance to one of two or more intervention arms or regimens. Randomization minimizes the differences among groups by equally distributing people with particular characteristics among all the trial arms.


the capacity of a vaccine to produce adverse reactions.


any chemical used in a laboratory test or experiment.


a molecule on the surface of a cell that serves as a recognition or binding site for antigens, antibodies, or other cellular or immunology components.

recombinant DNA technology

the technique by which genetic material from one organism is inserted into a foreign cell in order to mass-produce the protein encoded by the inserted genes.


the ability of an organism to develop strains that are impervious to specific threats to their existence. The malaria parasite has developed strains that are resistant to drugs such as chloroquine. The Anopheles mosquito has developed strains that are resistant to DDT and other insecticides.