States with strict vaccine exemption policies have lower incidence of vaccine preventable disease, whereas states with lax vaccination policies have higher incidence of disease, according to the findings in Health Affairs.

Study researchers found 18 states to have the most effective vaccine exemption policies, whereas nine states had the least effective policies. When researchers compared the rates of Bordetella pertussis in these states they found that the states with the most effective vaccination policies had 37.74 fewer cases of B. pertussis per 100,000 residents.

“States that had the most effective portfolio of policies had lower incidences of pertussis,” W. David Bradford, PhD, and Anne Mandich, a PhD candidate, of the University of Georgia, wrote. “Vaccine exemption policy is thus an important part of a comprehensive plan for reducing preventable diseases.”