Can confirm, I grew up near the area described in the article. USC has some 2010 data [1] on religious beliefs in Marin. None of the popular belief systems are known for discouraging immunization. Anecdotally, Marin has quite a large alternative medicine following which may explain the high opt-out rate.

[1] http://crcc.usc.edu/resources/demographics/marin.html

It's astounding to me that the anti-vaccine movement is so strong in Marin of all paces, good percentage educated overall, good tertiary education and pretty high income.

But, as they say, people will believe despite evidence or overwhelming evidence to the contrary. One can excuse religious people on the basis that their belief is based in faith rather than interpreting the data their way. What happens in Marin, among other places, is that people believe despite data showing otherwise.

In other words, people in Marin aren't saying, well, but I have faith that vaccines are bad, no they're saying we believe data says vaccines are bad. It's incomprehensible.