In February 2007 a bill was introduced to add the religious exemption to day care in Montana.

Opposition From DHHS defeated the bill.

Below are various sources of information [mostly rough notes] that was used to compile a booklet on natural immunity of unvaccinated children, based mostly on the idea that unvaccinated children must have at least as much immunity as was prevalent in the prevaccine era. And of course, for many diseases it is obvious that natural immunity continued to increase after the introduction of specific vaccines.