Idaho’s immunization “opt-out” numbers have doubled in just the past nine years, according to federal and state data.

And what’s more, these kindergarten opt-out numbers surged, even as kindergarten enrollment has stagnated. Kindergarten enrollment numbers dropped in the wake of the Great Recession, and are only starting to rebound.

As Idaho Education News reported last week, the state’s opt-out rate has grown significantly in the past two years, as parents decide to enroll their children in school without a full battery of immunizations. But additional data, collected by the federal Centers for Disease Control, suggest that the trend has been years in the making.

In 2009-10, Idaho’s kindergarten immunization opt-out rate was 3.8 percent.

This year’s opt-out rate reached 7.4 percent, according to data released last week by the state Department of Health and Welfare.

Meanwhile, the 2019 Legislature made it even easier for parents to exercise their legal right to opt their children out of any — or all — of the immunizations recommended by Health and Welfare. Lawmakers ratified a rule that allows parents to opt out simply by submitting a letter to their neighborhood school.

A separate bill — requiring schools and childcare centers to provide opt-out information to parents, at the same time they provide information on state immunization guidelines — passed the House, but Senate Health and Welfare Committee Chairman Fred Martin says he will not hold a hearing on it.

Idaho’s recent increase in opt-out rates could be — at least partially — a function of improved data collection. The number of “incomplete” immunization records has dropped over the past two years. This could account for some of the increase in opt-out rates, but not the entire increase.

Perennially, Idaho’s opt-out rates are still among the highest in the nation.

Idaho’s rates have ranked in the top three nationally every year since 2013-14, according to CDC data.

National rankings are not yet available for 2018-19.