Minnesota has seen one of the nation’s sharpest drops in measles herd immunity among kindergartners, falling well below the threshold needed to prevent outbreaks. A rise in nonmedical exemptions, especially at private schools, is one factor behind the decline.
New measles cases have been reported in Dakota and Olmsted counties since the beginning of the school year, raising Minnesota’s total to 24 confirmed cases in 2025. It’s one of the highest totals in two decades.
In the hopes of establishing an early warning system for outbreaks, the Minnesota Department of Health is starting to report measles detected in sewer samples, similar to the public health technique that emerged during the COVID-19 pandemic.
Since the pandemic, measles vaccination rates, usually administered via the MMR vaccine that also covers mumps and rubella and is required for incoming kindergartners, have fallen in most states.
In the last school year, the rates in some states dropped sharply, including Minnesota, Wisconsin, Alaska and Idaho. More than 15 states now have fewer than 90% of kindergartners vaccinated against measles, well under the recommended 95% threshold for herd immunity.
Minnesota experienced one of the biggest drops compared with its pre-pandemic level, from 92.5% to 86.5%, well below the U.S. average.
The steepest drops in kindergarten MMR rates have been in private and charter schools, according to data from the Minnesota Department of Health.
While full-vaccination rates at public schools dropped 6 percentage points, private schools’ vaccination rates dropped nearly 10, and at charter schools, it’s down nearly a dozen points.
