That's because the Centers for Disease Control and Prevention says the majority of people who contracted the measles weren't vaccinated.
So here's a step-by-step look at where children are getting vaccinated more, where they are getting vaccinated less – and what the rate looks like in Minnesota.
Minnesota compared to the US
The Wall Street Journal recently published a state-by-state analysis on how vaccination rates have changed over the years. In Minnesota, the number of 19- to 35-month-old children who didn't get their MMR (measles, mumps and rubella) shot has gone up – from 7.7 percent in 2006, to 9.2 percent in 2013.
Nationally, the trend is similar, with nearly half the states having worse vaccination rates in 2013 (7.5 percent) than in 2006 (6.9 percent).
Currently, Minnesota ranks 31st in the U.S. when it comes to how many kids are vaccinated, and MPR News says this is somewhat unusual for the state, which "regularly finishes near the top of these types of surveys."
Iowa is 11th, Wisconsin is 16th, South Dakota is 17th, and North Dakota is 35th.
In-state: 'Clusters' of unvaccinated kids
Vaccination laws vary by state (see map at right).
According to Minnesota Department of Health data, there were 70,972 students enrolled in kindergarten during the 2013-14 school year – 1.72 percent of them (about 1,221 students) were not vaccinated either by choice or for medical reasons.
Although most students are vaccinated, the few who aren't tend to be "clustered" in smaller school districts, the Pioneer Press reports.
And when a disease (such as measles) reaches a community or school where a bunch of people aren't vaccinated, that's when it can spread, the CDC says.
The clusters in Minnesota tend to be private or charter schools in the metro area, data from the MDH shows.
"It's something we're looking in to, but we're still in the infancy of exploring what may be going on in these communities," MDH epidemiologist Ben Christianson told the Pioneer Press.
A look at the data
In the 2013-14 school year, there were 16 Minnesota school districts where at least 10 percent of kindergarteners weren't vaccinated by choice – that's a rate which is considered inadequate to provide immunity against preventable diseases, the USA Today notes.
These districts all had a kindergarten enrollment of fewer than 100 students.
The five districts with the highest percentage of unvaccinated kindergartners, by choice:
- Prairie Creek Community School – 20 percent
- Southside Family Charter School – 18.18 percent
- Floodwood – 17.65 percent
- Menahga – 15.46 percent
- Win-E-Mac – 14.29 percent
Some additional tidbits:
- Thirty-two districts, most with kindergarten enrollment under 100, had 5-10 percent of kindergarteners not vaccinated by choice, MDH data shows.
- St. Paul, the state's largest school district in 2013-14, only had 1.06 percent of its kindergarteners opt out of vaccinations, which is about 44 students.
- The state's five largest school districts all had more than 98 percent of kindergarteners vaccinated.
- Several districts had 100 percent of kindergartners immunized.
Nationally, about one in seven public and private schools in the nation have measles vaccine rates below 90 percent, USA Today found.