Michigan is at risk.

That's the warning from public health experts as more and more schoolchildren are not getting basic vaccinations to protect them -- and all of us -- from preventable disease.

Michigan makes it easy to avoid immunization and after years of increasing public concerns over side effects and government intervention, the rate of those going unvaccinated is dangerously high.

Nearly 45 percent of Michigan residents now live in counties at risk of disease outbreaks, according to an MLive analysis of state data.

The risk is not just theoretical. It is very real.

A recent outbreak in Traverse City shut down a 1,200-student charter school for a week, infected students at 14 other school buildings in the region, and has sickened dozens of people and forced hundreds into quarantine.

The culprit was pertussis -- also known as whooping cough -- a disease once thought to be nearly eradicated.

But Grand Traverse County has an undervaccination rate six times the national average. And nearly 1 in 5 of the kindergarteners (17 percent) at the charter school, Grand Traverse Academy, had parents who signed waivers exempting the children from required vaccinations.

This map shows the U.S. states with the highest rates of kindergarten vaccination waivers.

Last week, the other shoe dropped in Grand Traverse: Two residents were diagnosed with measles, the most contagious disease known to man and one that can have serious complications.

It happened in Traverse City. It could easily happen in communities throughout Michigan.

Michigan has one of the highest vaccine-waiver rates for kindergartners in the country, three times the national median, according to the Centers for Disease Control and Prevention. And the number of kindergartners getting vaccine waivers is growing. In five years, it's increased 23 percent, the CDC says.

"Our vaccination rates in the state are going in the wrong direction," said Matthew Davis, chief medical executive for the Michigan Department of Community Health. "And if we are going in the wrong direction, we are in trouble."

The CDC warns outbreaks of vaccine-preventable diseases are most likely to occur where "unvaccinated persons cluster in schools and communities."

Such clusters exist in a third of Michigan public and private schools housing kindergartners -- that's more than 800 school buildings scattered across 68 of the state's 83 counties, according to the MLive analysis.

Many of those clusters are in affluent and well-educated communities, such as Traverse City, Troy, Grosse Pointe and Clarkston.

Those opting out of vaccines tend to be health-conscious families who buy organic food, give their children health supplements and are drawn to alternatives to Western medicine. They cite internet websites skeptical about immunizations and worry the risk of vaccines outweigh the benefits.

But, unwittingly, their growing numbers are creating a serious health threat.

"Michigan is one of the worst states in the country" in terms of vaccine-waiver rates, and communities with high waiver rates should be "very concerned," said Dr. Paul Offit, a leading authority on vaccinations in the United States and chief of the infectious diseases division at Children's Hospital of Philadelphia.

"When you have a fairly large number of people who are choosing not to vaccinate, that puts not only their own children at risk, but also everyone else's," Offit said.

Those particularly at risk include infants, pregnant women, the elderly, cancer patients and others with compromised immune systems.

Jennifer Smith, a spokeswoman for the Michigan Department of Community Health, said state health officials are "truly concerned about susceptible pockets where individuals are not protected from vaccine-preventable diseases. ... We know that these pockets put our broader communities at risk."

Waiver rates

MLive analyzed vaccination and waiver rates for Michigan's kindergartners for the 2013-14 school year, the latest data available. Public health officials say the kindergarten vaccination data is one of the best benchmarks for tracking immunization trends.

In Michigan, children entering kindergarten must show proof of immunization for measles, pertussis, polio, mumps, rubella, hepatitis B, chicken pox, diphtheria and tetanus -- unless a parent signs the waiver.

Michigan is one of 20 states that allows parents to obtain a waiver for reasons beyond religious or medical concerns.

In 2013-14, Michigan had the fourth-highest rate of kindergarten vaccine waivers in the nation, behind only Oregon, Idaho and Vermont, according to the CDC. Michigan's vaccine-waiver rate of 5.9 percent compares to the national median of 1.8 percent.

About three-quarters of the waivers in Michigan are obtained because of philosophical objections. The number of waivers in that category has increased 60 percent in the past five years, state data shows.

Health experts get especially concerned when a school, community or county has a waiver rate above 7 percent. That's because whooping cough and measles - the most contagious diseases - need an estimated 93 percent of the population to be resistant to those germs to prevent an outbreak if an infected person comes into the community.

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for students who have been vaccinated or were granted waivers, by school, district and/or county.

Michigan has 21 counties with a vaccine waiver rate of 7.1 percent or more among kindergartners.

Those counties contain 44 percent of the state's population and include Wayne, Oakland, Washtenaw, Livingston, Lenawee, St. Clair, Lapeer, Midland and Grand Traverse.

A number of individual school communities have double-digit waiver rates, including Bloomfield Hills, Birmingham, Northville and Rochester.

Some of the highest waiver rates are at private schools. At Cranbrook Academy in Bloomfield Hills, one of the state's most prestigious private schools, 23 percent of kindergartners had a vaccination waiver.

Based on state statistics, it appears about 150,000 of Michigan's public and private school students -- 6 percent of the K-12 population -- do not have all their required immunizations, which includes older children who did not get shots required after kindergarten.

As the number of vaccination waivers have grown, public-health experts say it's no coincidence that whooping cough is making a comeback in Michigan.

In 2002, the state had 62 cases of whooping cough. Last year, there were 995 cases, half of which were in children under the age of 12. In 114 cases, the patients were hospitalized. An Oakland County infant died of the disease in 2012.

A 2008 study found a geographic overlap between clusters of vaccine waivers and clusters of pertussis cases in Michigan.

Yet the threat of undervaccination is largely invisible to Michigan residents.

Most people have no idea how many parents do not vaccinate. They have no idea that their children, elderly relatives or friends with compromised health go to school or the grocery store in communities where vaccination rates are as low as those in Third World countries.

"The first question people ask me regarding the current outbreak of Enterovirus D-68 is 'Do we have a vaccine?' Same thing with Ebola," Davis said.

"How do we reconcile that question with our failure to use vaccines on a regular basis with our kids?" Davis said. "We have the ability to protect ourselves and our most vulnerable, and we are losing more babies to pertussis?"

Herd immunity

If people choose not to immunize their children, why is that a problem for anybody but those children?

It goes to the concept of what experts call "herd immunity."

For outbreaks to occur, germs must not only be introduced to a community, they must also encounter vulnerable people to infect. Those people must encounter other vulnerable people for disease to spread.

This chart shows the rise in pertussis, or whooping cough, cases in Michigan in recent years.

If enough people are immune, the disease is contained and an outbreak is prevented.

Each vaccinated person is not only protected from illness, but is one less receptive host for the disease to exploit. Each immune person helps create a protective bubble around the vulnerable few -- such as infants too young to be vaccinated, people with medical conditions that prevent vaccination, those undergoing cancer treatments or whose immune systems have been weakened.

"Of 314 million people in the U.S. about 500,000 cannot be vaccinated" for medical reasons, Offit said, "and they depend on those around them to protect them."

Moreover, because no vaccine is 100 percent effective, even if you and your children are vaccinated, you are still at some risk if an outbreak occurs.

"You cannot ignore the people who opt out (of vaccination) because you are going to come into contact with those people and that puts you at risk," Offit said.

In explaining the effectiveness of herd immunity, Offit cites a study in the Netherlands after an outbreak there.

"Surprisingly," Offit said, "you were (statistically) better off to be unimmunized in a high vaccine area than vaccinated in a low vaccine area because no vaccine is 100 percent effective, and in low vaccine areas a disease can catch on and spread quickly so your chance of exposure is greater."

The safety debate

There is widespread consensus in the scientific community that vaccines are safe and effective, and scientists say the fear vaccines are responsible for a rise in autism has been thoroughly discredited.

The American Academy of Pediatrics says immunizations "are the best way to prevent disease." The Centers for Disease Control says vaccines are "held to the highest standard of safety."

In 2011, the Institute of Medicine did an in-depth review of the current medical and scientific evidence on vaccines and vaccine adverse events, looking at eight vaccines given to children. The study found "these vaccines are generally very safe and that serious adverse events are quite rare."

This map shows kindergarten vaccination waiver rates by county in Michigan.

"The simple message is that vaccines save lives, millions of lives throughout history," said Dr. Jevon McFadden, medical epidemiologist at Michigan Department of Community Health. "They are the most important achievement in public health. They are a life-saving mechanism."

In 1920 alone, nearly 2,000 Michigan residents died of diphtheria, measles or whooping cough -- the equivalent to nearly 6,000 people based on today's population.

Many older Michigan residents still recall the terror of polio epidemics in the early 1950s, and the excitement when a polio vaccine was unveiled at a University of Michigan press conference in 1955.

Still, skepticism about vaccines dates back to the 19th Century, when the Anti-Vaccination Society of America railed against smallpox immunizations.

Back then, opposition to vaccinations was largely rooted in fears of catching the disease from the shot, which occurred in rare instances.

Today, opponents are more concerned the vaccines may contribute to long-term neurological problems, such as autism.

Among those questioning the conventional wisdom on vaccines is Marcel Lenz, a Traverse City resident who is father of children ages 4 and 2.

Lenz, who has a doctorate in horticulture, said he had a "falling out with Western medicine" and is persuaded by the arguments of alternative-health advocates who say vaccines are potentially harmful.

"I haven't seen the studies that convince me that vaccines are safe and effective," Lenz said, adding that it is his belief that diseases such as polio already were already on the wane before the vaccines were introduced.

Based on his reading, he said, "the probability of getting one of these diseases is low, and even if you do get something, it's probably not going to be that severe."

By contrast, he said, "every vaccine has components in it that are toxic that you don't want in the bloodstream."

"There are pros and cons to everything," Lenz said, "and I just don't trust vaccines."

Parents signing vaccination waivers say it's their right to opt out.

"I don't believe you can drug your way to good health," said Sue Waltman of St. Clair Shores, who founded Michigan Opposing Mandatory Vaccines in 1994.

"The most important thing is to keep your immune system strong through proper nutrition and hygiene," Waltman said. "You don't keep it strong by injecting your body full of disease. It's just so basic."

"If you want to vaccinate, go right ahead," she added. But "it's our right to make the decision not to do it."

Offit argues, though, that it is no one's right to catch and transmit a potentially fatal infection. "I think in a better society we wouldn't let it happen," he said.

Making the argument

In the debate over vaccinations, it is clear many public health officials and parents are talking past each other, says Mark A. Largent, associate dean of Lyman Briggs College at Michigan State University and author of the 2012 book "Vaccine: The Debate in Modern America."

"I share public health officials' belief in the value of vaccines to help protect both individuals' and the public health," Largent said. But "things that (public health officials) find a compelling argument are not the things (parents) find a compelling argument."

"Why aren't parents compelled by communal good? Because I don't (care) about public good, I care about my child," Largent said. "We need to say: 'You need to vaccinate your child because it is in your children's best interest,' not for the public good."

He says health officials need to directly address parents' issues, including the sheer number of vaccines required for babies and toddlers. The current vaccination schedule requires children get 22 shots in the first 15 months of life.

Largent also said "my-way-or-the-highway" doctors who blithely dismiss parents' questions and anxieties are also part of the problem.

While there are some parents who are anti-vaccine, "the bigger chunk are vaccine anxious," Largent said.

"We don't want the vaccine anxious to find refuge in anti-vaxers. We want to help parents feel the authorities are speaking to them, not at them," Largent said.

Largent said skepticism about science and mainstream medicine is also an issue. Much like debates over climate change, stem cell research and the teaching of evolution, Largent said, "no scientific finding and no agreement among physicians can bring it to a close because the debate is cultural and political, and only partially about science and medicine."

"I think there is a great deal of misinformation, particularly on the internet, and that has led some people to make the calculation that the risk of vaccine is greater than any benefit," McFadden said.

"We know vaccines are safe -- they are the most highly scrutinized and there is a significant surveillance effort ongoing that is unlike surveillance for any other medication," he added.

Health officials say that, in some ways, vaccines have become a victim of their own success.

"Today's parents have not seen tetanus or polio," Davis said. "There is a reason for that and that reason has a name -- vaccines. When we learn not to respect a threat, that threat comes back to challenge us. That's the challenge we face in Michigan."

Rosemary Parker is a reporter for MLive.com. Reach her at rparker3@mlive.com.

MLive reporter Julie Mack contributed to this report.