The Impact of Michigan's Nonmedical Vaccine Exemption Rule Change on Philosophical Exemption Rates.

To examine school factors associated with philosophical exemption rates among kindergarteners in Michigan from 2014, before Michigan's implementation of administrative rule 325.176 (12), to 2015, after the rule change revising the process for receiving nonmedical exemptions from school entry vaccines. The study explored the extent to which the factors-school type, geographical location, and socioeconomics-were associated with philosophical exemptions among kindergarteners before and after the rule change, using negative binomial regression and Spearman's Rho correlation. Philosophical exemptions decreased from 2014 to 2015 for all school types but remained highest among rural private schools. Urban private schools had the second highest exemptions with rates 2.22 times higher than those of urban public schools. Exemption rates among rural charter schools were double those of urban public schools, while rural public schools' rates were 1.22 times higher than those of urban public schools. Free and reduced school lunch eligibility had a strong inverse association with philosophical exemptions for both 2014 and 2015, with higher philosophical exemptions being associated with higher socioeconomic schools. Philosophical exemption rates decreased in the wake of the rule change; however, high philosophical exemptions, post rule change, were still associated with private schools, rural locations, and high socioeconomic status schools.