State and local public health officials say they are concerned about the rising risk of disease in schools as more parents across the state each year have opted their children out of otherwise mandatory vaccinations.

A growing number of parents in Plano ISD have filed for vaccine exemptions since 2003, when state lawmakers made it legal for parents to seek exemptions for reasons of conscience. Previously, only medical or religious reasons were considered.

Districts are required by law to report the number of conscientious exemptions to the Texas Department of State Health Services each year. In the 2015-16 school year, the most recent in which data was collected, the rate of PISD students who had filed for conscientious exemptions rose to 1.76 percent—more than double the state average.

The same pattern holds for other districts in Collin County, which has the 13th-highest exemption rate of the state’s 254 counties at 1.92 percent.

The trend, if it continues on its current trajectory, threatens to undermine what vaccine researchers call herd immunity. A population’s high vaccination rate helps slow the spread of vaccine-preventable diseases, protecting the unvaccinated and people for whom vaccines are not fully effective.

“The health services team is aware of the exemption rates in Plano ISD and Collin County,” PISD spokesperson Lesley Range-Stanton said in a written statement. “The district is prepared to respond to medical challenges that may arise, which includes working closely with Collin County Health Care Services and following guidelines set forth by the county and by the [state].”

Although the state health agency does not yet recognize a “significant concern statewide” as a result of the trend, an agency spokesperson said the risk of outbreaks increases as vaccination rates continue their steady decline in school districts throughout.

“There’s not a number that I think we can point to that at ‘X,’ it’s going to be a problem,” said Chris Van Deusen, a spokesperson for the agency. “It’s really kind of a sliding scale, if you will. The more unvaccinated individuals you have, the more likely you could have some sort of outbreak.”

In neighboring Denton County, where more than 2 percent of students countywide have received conscientious exemptions, a top health official says herd immunity is already being undermined.

“Having twice the state average, that’s a concern to us, because we believe vaccines are a good way to prevent communicable and infectious diseases,” said Matt Richardson, Denton County director of public health.

POLICY AND DEMOGRAPHICS

At least two proposals under consideration in the Texas Legislature this session would make it more difficult for parents to obtain an exemption. House Bill 241 would require a doctor’s consultation before parents obtain an exemption; HB 126 would require parents to first review online educational materials.

Another bill, HB 1124, would make it easier to obtain an exemption by making the relevant forms available for download on the state health agency’s website, simplifying the current multistep process that includes requesting a mailed form from the agency website and submitting a notarized affidavit to the child’s school.

Some groups have organized to lobby against legislative efforts to curb exemption rates, including Texans for Vaccine Choice, based in the North Texas suburb Keller.

“These bills would place a barrier between parents and their exemptions,” the group’s Director of State Policy Rebecca Hardy said. “These bills also assume the parents that are requesting these exemptions are uneducated, when in fact all the research shows that those that choose personalized vaccination schedules are, in fact, quite educated.”

A government study of data from the 2009 National Immunization Survey found parents who delay or refuse vaccinations for their children are more likely than the average person to have graduated from college and have a household income at least four times the federal poverty line, among other factors associated with higher socioeconomic status.

The Centers for Disease Control and Prevention analyzed survey responses from a sample of 11,206 children and determined children were vaccinated at lower rates across the board if their parents believed vaccinations could result in serious side effects or that too many vaccines could overwhelm a child’s immune system.

The study also found parents who delayed and refused vaccines are more likely to be white than those who neither delayed nor refused vaccines.

In Collin County, the median 2015 household income was $84,735, or more than four times the poverty level for a three-person household, according to U.S. census surveys. Nearly half of Collin County adults age 25 and older had at least a bachelor’s degree, compared to 30 percent nationwide.

Hardy, after citing a handful of examples of private and charter schools that have high exemption rates and no recent disease outbreaks, said her group promotes access to exemptions without weighing in on the scientific consensus on declining vaccination rates and herd immunity.

“They’re following their religious and other deeply held convictions,” Hardy said of parents seeking exemptions.

But state health officials say such examples of small populations that avoid outbreaks are not reflective of the broader risks associated with declining vaccination rates.

For an outbreak to occur, Van Deusen said, it is not enough to simply have low vaccination rates; the disease, made rare by the widespread use of vaccines, must also be reintroduced to the population.

LOCAL PROTOCOL

PISD officials have protocols for preventing and responding to outbreaks of disease.

The district provides information to parents, students and staff on how to prevent the spread of an illness, Range-Stanton said. In the event of an outbreak, the district would report the illness to health authorities and work with county and state health departments to temporarily remove vulnerable students from the population.

Although state law allows districts during an outbreak to send home exempt students without an excused absence, PISD may excuse the absences for any acceptable reason, including illness, quarantine or exclusion during a period of observation, Range-Stanton said.

The state agency that compiles the district exemption rates each year does not analyze it in great detail, leaving that up to independent researchers, Van Deusen said. And since there is no hard-and-fast cutoff for what exemption rates are considered too high, the state offers districts little guidance on that matter.

Because exemptions are allowed by state law, the state has limited tools for addressing vaccination rate increases, Van Deusen said.

“We can’t twist people’s arms and we can’t force vaccinations, because exemptions are a legal—that’s a right that people have,” Van Deusen said. “Obviously, we fall back on the science and we talk about the benefits of immunization and how important they’ve been over the decades, since they were one of the ultimate achievements of public health in the 20th century.”