Herd Immunity is defined as "the resistance to the spread of a contagious disease within a population that results if a sufficiently high proportion of individuals are immune to the disease, especially through vaccination."
Lets break that down a bit: Most people will make sure they are vaccinated against contagious diseases...but did you know that people who get themselves vaccinated against diseases are also creating protection for those who aren't vaccinated??
* Taken from iflscience.com
