The Asheville Citizen-Times reports that the percentage of kindergarteners in Buncombe County with religious exemptions from vaccination requirements has jumped to 4.22% for the current school year — five times the state average and well above the rate of surrounding counties.

It’s a trend that worries public health officials, and for good reason. When parents opt out of vaccinating their children, they endanger the community as a whole.

If at least 95% of a population is immunized, vulnerable members of the group are protected by something called “herd” immunity. This means that people who cannot be vaccinated, either because they are too young or pregnant or have a health condition, are protected because there is little opportunity for a disease to spread.

When herd immunity diminishes, outbreaks occur. Take, for example, whooping cough. Pertussis, a highly contagious childhood disease once conquered in the developed world, has made a dramatic comeback in recent years. Researchers studying a 2010 outbreak in California that resulted in ten infant fatalities and sickened more than 9,000 people found that outbreaks of the disease clustered in areas with high rates of personal belief exemptions. That year, only 91% of California kindergarteners were vaccinated.

Babies cannot be vaccinated for whooping cough until they are at least two months old, and the disease is particularly dangerous — sometimes fatal — for infants. Moreover, the vaccine wears off over time. Whereas previously people vaccinated against the disease as children could count on herd immunity to keep them safe as the vaccine grew less effective, loss of herd immunity makes people who have not received boosters vulnerable as well.

“It’s a matter of time until locally we see something like measles,” Buncome County DHHS medical director Dr. Jennifer Mullendore said.

Last spring, North Carolina dealt with its first measles outbreak in more than 20 years. Whooping cough has also made a comeback. In 2010, 68 cases were reported in Buncombe County.

Via the Citizen-Times:

“I think at the heart of the problem is that we’ve been so successful with preventing these diseases and because we’ve been so successful, families, parents, they don’t know what we’re preventing. They haven’t experienced it,” Mims said. She began noticing the high number of exemptions in Buncombe County when she was medical director for the county health department.

Citizen-Times – More Buncombe parents reject vaccinations

Vaccine exemptions are also on the rise statewide, increasing from 126 in 1999 to more than 1,000 for the current school year, according to the Citizen-Times report.