It absolutely is. The virus will kill off the Missourians who are susceptible to it, eventually leaving Missourians with genetic resistance to the disease, while other populations won't develop that resistance due to using the vaccine.

When, for whatever reason, there is an interruption in the ability to provide the vaccine, huge numbers of the non-Missourian population will die off, and the rest of them will be so weakened that the Missourians will be able to overwhelm them, take their land, and march them off to Oklahoma.