How common are vaccination exemptions for Minnesota's kindergartners?

A couple years ago, cultural conversation around vaccinations for young children was at its peak, and we published a database allowing readers to look up the rates for Minnesota's kindergartners at each school in the state.

It was so popular, we thought we'd revisit that data and see what else could be gleaned.

The Minnesota Department of Health collects vaccination data from Minnesota schools for kindergarten classes and seventh grade classes. We've chosen to focus on kindergartners since they have more mandated vaccines, and because they generally have a lower compliance rate than seventh graders.

Looking at the last four years of data from MDH, the vast majority of kindergartners are fully vaccinated every year. Among those who aren't, some are simply behind on their vaccination schedule, but some have gone through the extra work of acquiring a legal exemption.

There are two categories of a vaccination exemption – medical and non-medical.

Medical exemptions are extraordinarily low in number and are reserved for children who are considered too medically frail to receive vaccinations. Each year, there have been fewer than 40 such children in the whole state.

The other category, a non-medical exemption, is for a conscientious objection or philosophical aversion to vaccinations.

The number of kindergartners with a non-medical exemption for all vaccines was increasing every year until the 2015-2016 school year, when it went back down.

At the same time, the total statewide kindergarten enrollment has decreased, dropping by nearly 7 percent in the same time frame.

It's important to remember, however, that these students still represent less than 2 percent of Minnesota's kindergartners.

There are also some geographic trends.

Minnesota counties with the highest rates of kindergartners with non-medical exemptions are all in rural areas -- in Wadena and Hubbard counties, more than 8 percent of kindergartners have a non-medical exemption for all vaccines.

In the Twin Cities five-county area, the share is right around the state average. In a few surrounding counties – Carver, Scott, Isanti – the rates are higher by comparison.

Rural school districts are also the ones with the highest rates of kindergartners with non-medical exemptions. No students in these districts had medical exemptions from vaccines.

We've only included public school districts in this list, since private, parochial and charter schools are often counted as their own districts and have very small class sizes.

Now, these are exemptions for any and all vaccines. Parents can also get legal exemptions for their children for just one (or two or three) vaccines on the list for kindergartners, so if we break this out by individual vaccine, some groups of students have much higher numbers.

For example, at Rivertree School in Robbinsdale, nearly 43 percent of its 14 kindergartners last year had a non-medical exemption from the MMR vaccine.

High percentages of students without vaccinations can be dangerous when it comes to "herd immunity." When a significant portion of a populataion is vaccinated against a disease, they provide protection for those who have not gained immunity yet, or are unable to be vaccinated for medical reasons, by making it difficult for a disease to spread -- the "herd" is able to keep most of its members immune. But herd immunity is difficult to achieve if fewer people are vaccinated.

Search for your school below, but remember this is for last year's kindergartners. Data for this year's class isn't available yet.

The DTap vaccine protects against diptheria, tetanus and pertussis (whooping chough.) The MMR vaccine protects against measles, mumps and rubella. The Varicella vaccine protects against chicken pox.

Data Drop is a weekly feature that uses data analysis and visualizations to explain, surprise, inform and entertain readers on topics relevant to Minnesotans. Do you have an idea you'd like us to explore? Contact MaryJo Webster.