The measles outbreak at Disneyland, which came to the public's attention in January 2015, prompted several states to tighten their vaccine exemption laws. California, for instance, went from having one of the weakest laws in the nation to one of the strictest after it eliminated personal and religious objections for the parents of children enrolling in school or day care.

Even before the Disneyland outbreak, Michigan was in the process of tightening its vaccine exemption laws. According to MLive, a Michigan news site, the state made it very easy for a parent to obtain an exemption. Unsurprisingly, the CDC reports that in the 2014-15 academic year, 5.3% of Michigan's kindergartners had an exemption.

In December 2014, however, Michigan lawmakers set about making the state's vaccine laws tougher. As of January 1, 2015, parents seeking an exemption had to discuss vaccines with a healthcare worker and then sign a waiver which declared that they were still willing to put their child and others at risk.

The latest CDC data shows that, for the 2015-16 school year, the exemption rate among Michigan's kindergartners fell to 3.6%. Thus, the state's policy appears to be working, possibly for two reasons.

First, MLive states, rather shockingly, that some parents find it more convenient to get a waiver than to take their children to the clinic to get a shot. Some parents choose not to vaccinate, not out of medical or philosophical concerns, but out of sheer laziness. If the government makes exemptions are harder to obtain than vaccines, then vaccination rates should increase. Second, explicitly warning parents that their decision is endangering their children may make them think twice.

Notably, while Michigan witnessed a 1.7 percentage point drop in exemption rate (the 2nd highest in the nation)*, the U.S. as a whole saw the median exemption rate increase by 0.2 percentage points.

Apparently, preventable infectious diseases still don't scare many people.

Source: Seither R, Calhoun K, Mellerson J, et al. "Vaccination Coverage Among Children in Kindergarten — United States, 2015–16 School Year." MMWR 65 (39): 1057–1064. DOI: 10.15585/mmwr.mm6539a3.

*The largest decrease in exemption rates occurred in Wisconsin, which experienced a 2.0 percentage point drop. However, it does not appear as if Wisconsin has new vaccine laws. (A tougher vaccine exemption bill was introduced into the state legislature in January 2016, but it failed on April 13.) Instead, the drop may be an artifact attributable to Wisconsin's sampling methodology.