Weaker non-medical exemption policies reduce likelihood of measles outbreak: Study

According to a new study, places which have weaker non-medical exemption policies for vaccinations can reduce the likelihood of a measles outbreak 140 to 190 percent by strengthening them.

The research was published in Academic Pediatrics.

The researchers also found, that the magnitude of these outbreaks can also be cut in half by strengthening exemption policies for children.

"In the year 2000 measles was no longer being transmitted in the U.S. Compare that to 2015 when we had over 150 cases in the first three months. Suddenly measles is an issue again despite having an effective vaccine," said the study's lead author Melanie Whittington, PhD., a health services researcher.

Using mathematical models, they simulated the magnitude, likelihood and cost of a measles outbreak under different non-medical vaccine exemption policies.

The states with "easy" exemption policies typically only require a parent signature on a standardized form.

Those, with "medium" exemption policies require parents to obtain a form from a health department and/or attend an educational session on vaccinations, or write a statement of objection.

Finally, states with "difficult" exemption policies require parents to get a standardized form or statement of objection notarized.

Using data from the Centers for Disease Control and Prevention's National Immunization Study, the researchers found easier non-medical vaccine exemption policies to be associated with a greater risk for outbreaks of vaccine-preventable diseases.

"We modeled an environment where the population had low vaccination coverage and then simulated measles outbreaks under different exemption policies," said Whittington.

Adding, "We found that a state like Colorado is 140 to 190 percent more likely to experience an outbreak with an easy exemption policy than if it had a medium or difficult non-medical exemption policy. The outbreak size can also be reduced nearly by half with stronger policies."

Colorado has one of the lowest vaccination rates for measles. Only 87.4 percent of children between the ages of 19-35 months are covered. And five percent of kindergartners report an exemption.

While the researchers focused on measles, strengthening exemption policies could benefit other vaccine-preventable diseases, such as mumps.

The researchers urged the strengthening of non-medical exemption policies as a way to increase vaccination coverage.

"We are not saying you can't have non-medical exemptions. But if we strengthen them, we can improve health and reduce the economic impact of a potential outbreak," said Campbell and Whittington.