Usually it's the "all-natural all vegan no GMOs I hate big pharma" types who reject vaccines. These kinds of people tend to be quite socially liberal. Your run of the mill Evangelical Christian is not this. Having spent my entire life in the Evangelical Christian community, I've yet to come across someone IRL who refuses to get their kids vaccinated. I'm sure there is a fringe group somewhere out there which, for example, associates vaccines with the mark of the beast, but if they exist then their numbers would be few.