Weakened. Attenuated viruses are often used as vaccines because they can no longer produce disease but may still stimulate a strong immune response. Examples include vaccines against polio (Sabin oral vaccine), measles, mumps, and rubella.
Weakened or thinned. Attenuated strains of disease-causing bacteria and viruses are often used as vaccines. The weakened strains are used as vaccines because they stimulate a protective immune response while causing no disease or only mild disease in the person receiving the vaccine.
weakened. Attenuated viruses are often used as vaccines because they can no longer produce disease but still stimulate a strong immune response, like that to the natural virus. Examples of attenuated virus vaccines include oral polio, measles, mumps, and rubella vaccines.
weakened; with reference to microbiology or virology, to decrease the effectiveness, or virulence, of a pathogen. When a vaccine is attenuated, it means that it contains a weakened virus. This procedure is commonly used to induce active immunity in the body without causing illness. [Source: Biotechnology Industry Organization, www.bio.org
To be weakened. An attenuated vaccine is one that has been weakened by chemicals, or other processes so that it will produce an adequate immune response without causing the serious effects of an infection.