Herd immunity is a key component of public vaccination campaigns that keep everyone healthy and safe from preventable diseases. 538 did an article on this topic recently, and included a reference to FRED.
FRED is pretty interesting. You can pick a location and view the impact of a Measles case over time. With an 80% vaccination rate, measles cases soar. With rates of >95%, though, a case doesn’t spread. The importance of high vaccination rates is pretty clear.