New research on how to reduce the number of unvaccinated children

Adding more steps to opt out of mandatory vaccinations could cut the number of unvaccinated children, according to new UW-Madison research.

Researchers from the university’s Applied Population Laboratory analyzed how a law change in California affected the rate of unvaccinated children in kindergarten.

The state passed AB-2109 in 2012 in response to spiking rates of parents exempting their kids from vaccines. That law required parents who wanted an exemption for their kids — for a reason other than religious belief — to get the signature of a health care provider who could first explain the risks of doing so.

The UW-Madison researchers found that after the law was passed, the proportion of unvaccinated children entering kindergarten in California fell. The exemption rate dropped from its peak of 3.3 percent to 2.7 percent in the two following years.

However, the law change wasn’t a perfect fix, as the reduction was modest and didn’t really get at the heart of the problem: groupings of unvaccinated kids all going to the same schools. That clustering can lead to outbreaks.

Despite the drop in exemptions, the “isolation index” didn’t move much. That captures the probability that one unvaccinated student will run across another unvaccinated student. It fell from 16 percent to 15 percent.

That’s up from 10 percent at the beginning of the study period, which began during the 2001-2002 school year.

“So we saw a dent in exemptions, but not really in clustering,” said Malia Jones, the lead author of the new study and an assistant scientist in the Applied Population Laboratory. The lab is within UW-Madison’s Department of Community and Environmental Sociology.

Jones also collaborated with scientists from the University of Pennsylvania, Johns Hopkins University and Emory University. They used state population data, including info on public and private schools. Only kindergarten classes with fewer than 10 students were excluded.

The study was published earlier this month in the journal Health Affairs, and she presented the results earlier this week at a briefing in Santa Monica.

Though California’s situation provided a good example for study, Wisconsin has also seen a rise in unvaccinated kids in recent years. The La Crosse Tribune reported in 2015 that over a quarter of Wisconsin schools have vaccination rates below 90 percent, slightly lower than the rate needed for the protective benefits of herd immunity for measles.

And a Washington Post report from this year found Bayfield County is one of the top 10 counties in the nation for non-medical vaccine exemption rates, with over 16 percent. Eight of the other top 10 were in Idaho, while one was in Utah.

Following a widely publicized measles outbreak at Disneyland in 2014, California passed SB-277 in 2015 to eliminate personal belief exemptions. That led to exemption rates falling “substantially,” according to a UW-Madison release.

For other states that don’t want to ban exemptions entirely, but would like to make it more difficult to get one, Jones says California’s AB-2109 bill could provide a model.

“Making it a little bit harder to get an exemption is a much more feasible strategy for most states,” she said.

See the study: