HERDIMMUNITY

Herd immunity

Herd immunity describes a form of immunity that occurs when the vaccination of a significant portion of a population provides a measure of protection for individuals who have not developed immunity. Herd immunity theory proposes that, in contagious diseases that are transmitted from individual to individual, chains of infection are likely to be disrupted when large numbers of a population are immune or less susceptible to the disease. The greater the proportion of individuals who are resistant, the smaller the probability that a susceptible individual will come into contact with an infectious individual.

The above text is a snippet from Wikipedia: Herd immunity
and as such is available under the Creative Commons Attribution/Share-Alike License.

Need help with a clue?
Try your search in the crossword dictionary!