The number of schools in Minnesota where the measles and chickenpox vaccination rate is low in kindergarten has risen sharply over the last five years, which has worried health officials of their state of vulnerability to outbreaks of highly contagious diseases.

One-third of Minnesota schools had maternal immunization rates below the level required for "herd immunity," according to a Star Tribune analysis of 1,110 elementary schools.

According to the Minnesota Department of Health, many of these schools have had chickenpox outbreaks since 2017, including one that has had two separate outbreaks.

Unvaccinated children also contributed to a measles epidemic in 2017, which rendered 75 patients sick and sent 21 to the hospital. According to the US Centers for Disease Control and Prevention, measles cases have been resurrected in pockets of countries with low immunization rates, with nearly 400 cases last year.

"We are concerned about these children," said Dr. Sheldon Berkowitz, president-elect of the chapter of the American Academy of Pediatrics in Minnesota. "It's important to vaccinate not only your own child, but also other children in the community who are not able to get vaccinated."

Declining immunization rates have caused concern among groups of physicians, public health officials and researchers who remind the public that vaccines pose low risks and are good for the health of the population. They cite numerous medical research, including a recent study that revealed that there was no link between measles vaccine and autism, one of the myths that drove down the rates and fertile ground for the recent measles outbreak in Minnesota.

"I think fear, the Internet and the idea that there is no scientific basis in the recommendations we make are the driving force," Berkowitz said. "In fact, they rely on very solid scientific information."

Minnesota public health officials are concerned about this trend, but note that vaccination rates across the country are high: 93% for measles and 92% for chickenpox.

"When you have your children vaccinated, you are the norm," said Kris Ehresmann, director of infectious diseases in the Department of Health. "People who do not vaccinate … are a small aberration but an aberration that has grown, so we are worried about it."

Of the 787 schools that have kindergartens, the measles vaccination rate was equal to or higher than the 90% recorded for the 2017-2018 school year, the most recent data available. Together, they enroll four-fifths of the state's children.

But these numbers mask the pockets of lower rates where diseases can spread easily close up.

The trend is partly motivated by the increasing number of parents who choose not to vaccinate their children, as permitted by law, but who may also include children receiving incomplete doses or whose parents have not completed the paperwork required.

Whatever the reason, more schools are now falling below 90% of the measles, mumps and rubella (MMR) vaccine rates. Last year, it was 30% of all children's gardens, compared to 22% five years earlier. During this period, 150 schools saw their vaccination rates fall by more than 5 percentage points, bringing them below the 90% level.

For chicken pox, 33% of schools have a level of immunity below the 90% immunity threshold, which, according to public health authorities, is the lower limit needed to prevent epidemics.

Schools report immunization rates for kindergarten and grade 7 students only. Vaccination rates improve at the higher level, where only half of the schools are below the 90% threshold set for MMR and chicken pox.

Many of these pockets are in small private charter schools, where a handful of unvaccinated children from a small maternal population can lower the vaccination rate below the recommended threshold.

Nevertheless, one-fifth of state children are enrolled in these "pocket" schools, and although most of these children receive the two recommended doses of MMR vaccine, they are also at risk because it does not offer complete protection.

"Put us on alert"

In addition to the risk of an epidemic, students without bullets can put other children at risk who can not be vaccinated for medical reasons. Many of these children have weakened immune systems caused by chronic illness or medical treatment. Getting a vaccine such as MMR, which contains a living but weakened form of the virus, could actually make them sick. And if they contracted the disease from someone else, they would probably develop severe symptoms.

"It's something we think about all the time," said Linsey Rippy, who has two daughters who have had a heart transplant. They take drugs that prevent their bodies from rejecting their heart, but these medications also undermine their ability to fight diseases.

"People around my children need to be vaccinated, so we know we're giving them the maximum safety net possible," Rippy said.

At the beginning of each school year, Rippy writes a letter to her children's teachers and asks them to pass it on to all parents about the importance of immunization. "It's not up to me whether their children are vaccinated," she said. "But at least I hope they understand a little more about what we went through and why we feel like ourselves."

While measles epidemics have recently been reported throughout the country, revealing a growing reluctance to vaccinate parents, Rippy fears that schools will lose the immunity of the flock that protects her children.

"It puts us on alert," she said.

Minnesota is one of 17 states that allow parents not to be vaccinated for personal reasons. All states provide exemptions for medical reasons, while others state that exemptions must be based on religious beliefs.

Kelly Johnson, whose 12-year-old daughter is in public school and has never been vaccinated, is one of the skeptics.

"I just filled out the conscientious objector form," Johnson said. "It's a right that Minnesota parents have."

Johnson began questioning the vaccines after his eldest daughter began having seizures at a young age. She believes that the MMR vaccine was responsible, but she also traces other medical problems, including chronic ear infections, in vaccines received by her daughter at the age of 2 months.

The crises have never stopped and today, his 20 year old daughter is in a wheelchair.

Johnson also has a 21-year-old son who has been vaccinated and has had health problems, including asthma and severe allergies.

"I have this little careful study in my own household and it's fascinating to see how much my unvaccinated child is healthier," she said. "I think we have the right, as parents, to do what we feel we should do for the health of our own children."

One school, two outbreaks

The growing number of schools where varicella vaccination does not conform to standards coincided with an acceleration of the onset of the disease.

The Maranatha Christian Academy in Brooklyn Park is one of four schools to have been affected by chicken pox in 2017. With 84% of its preschool and seventh-grade children immunized, including those who acquired Immunity following an illness, the school has been affected seven times.

By 2019, immunity in Maranatha had increased to 92% for kindergarten children and 90% for seventh grade students, but the school experienced another epidemic, this time nine cases.

"I do not want these diseases to come back to schools," said school principal Brian Sullivan in an interview.

Increasingly, Sullivan said, vaccinations have become a polarizing issue among parents. "It's a difficult situation. The law allows parents to withdraw, "he said. "We can not usurp their authority."

Sullivan said he had heard some concerns from parents about other people who chose not to vaccinate.

The role of the school is primarily to gather documentation on parental injections or exemptions and to inform the school community of any health problems, such as epidemics.

"We are limited by the parameters of the law," he said.

Last year, Eagle Ridge Academy, a charter school in Minnetonka, had documents on MMR immunization for only 66% of the 136 children enrolled in kindergarten.

"We have a large Somali population and this community is convinced that it has perverse effects, especially the ROR," said executive director Jason Ulbrich. "It's just wrong."

To improve the notification rate, the school organized parent meetings prior to the current school year to explain the importance of vaccines. Since then, rates have improved by 10 to 15 percent, he said.

"We try to educate them and put the information in their hands," Ulbrich said.