If you’re worried about ‘herd immunity’ protecting you from infection, you’re fairly safe in Crawford County. Immunization rates are running at 81-percent, according to Gloria Wall, the Crawford County Public Health Director.

The percentage comes, despite a slight dip in the MMR vaccination (Measles, Mumps and Rubella), and is still below the state average of 84.34-percent.

“I feel we are doing a much better job in Crawford County than we were 20 years ago,” Wall said.

However, a quick jaunt north to Vernon County, and those immunization rates drop precipitously to 54.29-percent, which by protection standards developed by the Center for Disease Control and Prevention has potential for a significant outbreak. It also falls well short of the federal government’s immunization goal of 90-percent.

Wisconsin is among the states that allow parents to opt out of immunizations for students attending public school for non-medical reasons. And like other states that allow opting out, a decline in the MMR vaccination rate has occurred.

So who is opting out?

Higher income whites are the ones opting out, according to Wall. It’s not the Amish, as some people believe.

“In Crawford County, we go to a site for the Amish every other month,” Wall said. “This was requested by the Amish. They contacted us and asked if it was possible. They have some students attending North Crawford School, which I believe is how they became aware of the program.”

Wall noted that there were some people in the county opting out of vaccination, but they are a very small number of people.

Those who are opting out are in some cases doing so selectively, hence the greater drop in MMR vaccination rates than in polio vaccinations. However, some are foregoing all immunizations.

Why are people choosing to not have children vaccinated?

A few are from medical necessity. Children under six months and any young medical patient on some form of immunosuppressant are unvaccinated or under-vaccinated, by CDC standards. Children and young adults with leukemia or other forms of cancer, children with juvenile rheumatic arthritis, Krohn’s disease, degenerative eye diseases, etc. have to abstain from vaccination just as they have to abstain from contact with actively ill people.

Yet, a large number of parents opting out of vaccinations are doing so primarily for nonmedical reasons.

Arguments against vaccinating children include the oft-mentioned belief that vaccinations increase the likelihood of autism spectrum disorders. Additionally, some people feel that natural immunity achieved through the body’s response to active disease is more effective than an immune response developed through non-active or a less virulent strain of a disease.

“Who wants to give their child four shots in a day?” asked Bridget Pfaff, Administrative Director of Infection Control at Gundersen Healthcare in LaCrosse. “Many parents don’t want to expose their child to that many antigens at once.”

Antigens are substances that stimulate the production of antibodies. However, Pfaff noted, we are in fact exposed to hundreds of antigens daily and she sees no difference in the level of immunity acquired from either the vaccine or the disease.

For parents worried about possible negative effects from multiple vaccinations, she suggested working with a pediatrician or family practitioner to space out vaccinations rather than forgoing them.

“Parents today haven’t seen the devastating affects of polio, they don’t know what measles looks like, they haven’t heard the stories of what it was like to live with these illnesses, how they impacted the community,” Pfaff noted.

The decision to vaccinate or not vaccinate is often made from a very personal view of one’s own child and not the larger community, Pfaff noted.

“Very few of us have witnesses a true pandemic or outbreak,” Pfaff said. “All to often, we are a population insulated from infectious disease.”

What does the herd immunity, often referenced by public health officials, actually mean?

Just as a herd of cattle protects its members from predators through sheer numbers, the concept of herd immunity is protection of a community from infectious diseases through the numbers of people immune to such diseases. The more members of a human ‘herd’ who are immune to a disease, the better protected the whole populace will be from an outbreak of that disease.

There are two ways an individual can become immune to an infectious disease: by becoming infected with the pathogen that causes it or by being vaccinated against it.

Because vaccines induce immunity without causing illness, they are considered a comparatively safe and effective way to fill a community with disease-resistant people, though immunity is not conferred 100-percent of the time.

The ‘herd immunity,’ or critical mass, is the percentage needed for protecting the unvaccinated, under-vaccinated and elderly. This percentage varies with the illness. Mumps only needs 75 percent of the population to be immune through vaccination to effectively protect the community members by preventing the chain of disease from reaching them and limiting potential outbreaks. Two doses of mumps vaccine are 88-percent (range: 66-95 percent) effective at preventing the disease.

Pertussis (whooping cough) requires 92 to 94-percent vaccination rates. And neither the vaccination nor the active disease confers lifetime immunity.

“We had more exposure to antigens in the past, in large part from our greater exposure to working with and living around animals,” Pfaff said.

Vaccines have replaced those exposures.

“We just aren’t seeing the constant small exposures, so immunizations provide that,” Pfaff said.

But through scientific trial and the review process, the exposures created with vaccines are much less likely to come with complications, according to Pfaff.

Wisconsin so far has avoided any confirmed cases of measles.

Pertussis? Well, that’s another story. Wisconsin has made headlines many years running as having one of the highest pertussis rates in the country. But it’s not whooping cough season. And yes, it has a season, the one we call summer…that was polio season too, though that disease is near eradication. The last naturally occurring case of polio in the U.S. was in 1979.

A global effort to eradicate polio began in 1988, led by the World Health Organization, UNICEF, and the Rotary Foundation. These efforts have reduced the number of annual diagnosed cases by 99-percent. All of the industrialized nations were polio-free, as of 2014. Civil unrest in parts of Africa has helped lead to its re-emergence in several countries. That paired with its continued transmission in Afghanistan and Pakistan led the World Health Organization to declare the disease remains a world health emergency in May of 2014.