attenuated virus

[ ə-tĕnyōō-ā′tĭd ]

n.

A strain of a virus whose pathogenicity has been reduced so that it will initiate the immune response without producing the specific disease.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.