California's elimination, in 2016, of non-medical vaccine exemptions from school entry requirements was associated with an estimated increase in vaccination coverage at state and county levels, according to a new study published this week in PLOS Medicine by Nathan Lo of the University of California, San Francisco, and colleagues.

Vaccine hesitancy, the reluctance or refusal to receive vaccinations, is a growing public health problem in the United States and globally. The effectiveness of state policies that eliminate non-medical exemptions to childhood vaccination requirements has been unclear. In the new study, researchers used publicly available data from the US Centers for Disease Control and Prevention on coverage of measles, mumps, and rubella (MMR) vaccination and rates of both non-medical and medical exemptions in children entering kindergarten. The dataset included information on 45 states from 2011 to 2017 and county-level data from 17 states spanning 2010 through 2017.

The results of the analysis suggest that after the 2016 implementation of California's new exemption policy, MMR coverage in California increased by 3.3% over what the projected MMR coverage in California would be in the absence of the policy. Non-medical vaccination exemptions decreased by 2.4% and medical exemptions increased by 0.4%. Change in MMR vaccination coverage across California counties from 2015 to 2017 ranged from a 6% decrease to a 26% increase, with the largest increases seen in "high risk" counties with the lower pre-policy vaccination coverage.

"These study results support the idea that state level governmental policies to remove non-medical exemptions can be effective strategies to increase vaccination coverage across the United States," the authors say.