I highly doubt people in Marin are doing it on religious grounds.
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.