In some areas the percentage of unvaccinated is quite high. See this map of anti-vaxxers by county http://rpubs.com/markdg/AntivaxxerHotspots
It uses the Personal Belief Exemption for school children as a proxy for the general population of anti-vaxxers. So arguably a bit inaccurate.
> It uses the Personal Belief Exemption for school children as a proxy for the general population of anti-vaxxers. So arguably a bit inaccurate.
Well, also there's been a lot of news events around the issue since 2015, which led to the elimination of the exemption, so its quite possible there have been signficant movements in attitudes in the last three years.
So, overall, a tiny minority; sure, it's a somewhat less tiny minority in some counties (and a significant one in a few) but those are mostly very low population counties, too.
State-wide that's true. But herd immunity is a local issue. So if your kid is going to a school where more than 10% of the other kids are unvaccinated then they won't benefit from herd immunity, despite the fact that the number of those unvaccinated kids is a tiny minority of all California kids.
I was also a bit shocked when I saw how high the Personal Belief Exemption was in some counties. Above 5% unvaccinated pretty much destroys herd immunity. So most of northern California is a no-go zone for people who appreciate the value of herd immunity.
What I have not seen, but would like to, is data for other states.
Fortunately, the highest-population counties in northern California are not too high - the number of schoolchildren in such counties is much lower that this map would indicate.