http://time.com/3514056/vaccine-rates-numbers-news/
Vaccination rates need to reach or exceed 95%, depending on the disease,
to maintain herd immunity—the protection afforded by vaccinated people to those few who can't be vaccinated, by giving the virus too few ways to body-surf its way across a population until it finds someone who's vulnerable. So while a 90% vaccination rate might look like an A, it in fact may be no better than a middling C.
And in some parts of the country, the numbers are much, much worse.
As I reported in TIME's Oct. 6 issue, vaccination refusal tends to be a phenomenon of the wealthier, better educated, politically bluer parts of the country—the northeast, the Pacific coast and pockets around major universities. Those are communities in which folks know just enough to convince themselves that they know it all—which means they know better than the doctors, scientists and other members of medical community at large, who have overwhelmingly shown that vaccines are safe and effective.