After Amy Nemeczky's youngest son was born, she had him vaccinated just as she had her older kids.

The babbling baby named Nate was in and out of the doctor's office that first year with upper respiratory and ear infections. Nemeczky was worried about Nate receiving more vaccines while he was ill, but she followed the doctor's advice that he get them. It's a decision she now regrets.

"He was never the same," she said of her son, who was later diagnosed as being on the autism spectrum.

The Frisco mother of three stopped getting most vaccinations for him and, later, her two older daughters.

More and more parents like Nemeczky are forgoing vaccines. Many do so because of concerns about a supposed link to autism, even though years of research have debunked that notion — a conclusion supported by the Centers for Disease Control and Prevention, the American Academy of Pediatrics and the National Institutes of Health, among others.

But politics and lax state laws have allowed the opting out to rise, making some areas in North Texas breeding grounds for outbreaks of diseases long thought eradicated.

And much to health officials' chagrin, a course reversal doesn't appear likely; a small but growing and powerful movement has stymied efforts to force more vaccinations and to allow parents to easily find out how many of their kids' classmates aren't immunized.

"It's so frustrating because I can see this train coming two miles down the tracks," said Dr. Peter Hotez, director of the Texas Children's Hospital Center for Vaccine Development and dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston. "And I can't do much to stop it other than just try to talk about vaccines, why they're safe, why the evidence shows there's clearly no link between vaccines and autism."

Pockets of resistance

Texas law requires children to be given vaccines, at different ages and school levels, for diphtheria, tetanus, pertussis, polio, measles, mumps, rubella, hepatitis A and B, varicella and meningococcal disease.

Sometimes families need exemptions for medical reasons, such as concerns that the vaccine would further harm immune systems weakened by chemotherapy or organ transplants.

But parents can also object because of personal beliefs. And some families, who fear the growing number of vaccines, opt for some shots and not others. Nemeczky, for instance, got Nate a varicella vaccine to protect him after she got shingles.

Related: Trend of no vaccines worries doctors

Hotez’s research has showed big clusters of exemptions in the western part of the country and in pockets where parents have slightly more wealth and education. His study showed Texas had the most “hot spots” of kindergartners whose parents, for nonmedical reasons, kept them from getting vaccinations against diseases such as measles, mumps, chicken pox and whooping cough.

Texas is among 18 states that let families opt out of vaccines for personal or moral beliefs, according to the National Conference of State Legislatures. And Plano, Fort Worth, Austin and Houston all ranked among the 15 U.S. metro areas with the most such conscientious exemptions for kindergartners. Each had more than 400 kindergartners exempted from vaccines.

Conscientious objections have risen steadily in the state over the past five years and now top 1 percent for the first time in recent years. Texas reported that 56,738 students — from kindergarten to 12th grade — opted out last school year. That’s an increase of almost 4,000 students from the previous year, according to the Texas Department of Health and Human Services.

Hotez, who is the father of an autistic daughter, is most concerned about how exemption hot spots can put more people at risk for outbreaks of childhood infections. He said people tend to look at national and statewide rates and say, "They're not that alarming."

But those numbers, he said, “mask pockets in these schools.”

A large majority of the schools with the highest exemption rates are private ones, although those schools tend to have fewer students. Among the 39 entities reporting rates of at least a 10 percent, all but four were private schools.

But private schools have no uniform policies. Some families may have religious objections, which could be reflected in larger numbers at a specific school. Catholic schools, however, don’t allow conscientious exemptions.

Among public schools, suburban districts tend to have higher numbers of conscientious objections. Frisco came in third in Texas with 1,266 children exempted, while Plano was seventh with 1,034.

Plano and Frisco school officials said they share immunization information with parents. While there have been some reported cases of illnesses such as whooping cough in Collin County, officials say they haven't seen significant effect on schools or absenteeism rates.

Districts alert parents when a notable outbreak occurs on a campus. But access to information about who has been vaccinated and who hasn't is limited because of federal privacy laws.

Officials in Plano ISD, for example, say they adhere to state reporting requirements on immunization coverage but don't share the information at the individual campus level. Frisco ISD officials say campus-level information is available to those who submit public information requests.

Frisco schools spokesman Jamie Driskill said that immunizations are "a sensitive topic for a lot of people on both sides of the issue," and that the district urges parents to "work with their health care providers to make the best decision for their family."

1 / 3Dawnn Walker prepared to administer an immunization at the Dallas Mayor's Back to School Fair on Friday at Fair Park in Dallas.(Louis DeLuca / Staff Photographer) 2 / 3Vials of immunization medicine are pictured at the Dallas Mayor's Back to School Fair.(Louis DeLuca / Staff Photographer) 3 / 3A nurse prepares to administer an immunization at the Dallas Mayor's Back to School Fair.(Louis DeLuca / Staff Photographer)

Herd immunity

Anali Morales of Dallas didn't think she'd be the kind of parent to vaccinate. But on Friday she stood in a long, winding line at a back-to-school fair in Dallas to get shots for her 3-year-old.

A college English assignment had required Morales to write a paper exploring an opposing view. She changed her position after learning about herd immunity. That's the community benefit — including to those who aren't vaccinated — when there are widespread immunizations that significantly decrease the risk of spreading illnesses.

"I prefer to be on the safe side — for my kids and to help others," Morales said. "It's better to have it. Even if there's an outbreak, having the vaccinations in your body will help you fight it."

Outbreaks have popped up in some of the pockets of exemptions.

Tarrant County has been hit the hardest in the state with whooping cough, or pertussis, in the last five years. It had a high of 700 cases in 2013 and 337 in 2016, which accounted for a quarter of the state's cases. Dallas County reported 99 cases and Collin County 82 in 2016.

"We've had more than our fair share of cases," Tarrant County epidemiologist Russ Jones said. "When we do see some schools with lower coverage rates, it can go like wildfire."

Jones noted that provisional results showed 496 cases for 2017 but only 123 through June of this year.

He said that exemptions, particularly in the more suburban northern parts of the county, are partly to blame. But he said the pertussis vaccination also isn't as effective as others.

Still, he said, evidence shows that the pertussis vaccine is key to preventing deaths and minimizing hospitalizations.

The young and the old are the most vulnerable. Tarrant County had one infant death related to whooping cough last year and one in 2008.

Overall, the state has fluctuated in the number of cases, from 954 in 2006 to 1,286 in 2016. Texas peaked in 2013 with 3,985 cases reported.

Some diseases, like measles, are more dangerous than they used to be generations ago.

Outbreaks of measles — once considered eradicated from the United States — are still rare. In 2016, the most recent year for which data was available, Texas reported only one case: an unvaccinated Collin County elementary school student who had traveled internationally.

In 2015, the state's only measles case was reported in Tarrant County. Two years before that, that county had experienced an unusually high number of cases at 16.

Mumps is uncommon, too, with maybe one or two cases reported in a county each year. But in 2016, Tarrant County reported 16 cases and Dallas 13.

The politics of medicine

Political trends have run counter to public health concerns. The North Texas-based Texans for Vaccine Choice has accumulated political power since its 2015 founding.

The group is well-funded, with numerous small and regular contributions and some big checks from wealthy business people, including $90,000 from Farris Wilks, the Cisco fracking billionaire.

In the last few years, the group has targeted key lawmakers that it saw as unfriendly to its cause. Legislators whom the group campaigned against included ousted Rep. Jason Villalba, R-Dallas, and Sarah Davis, a Houston-area Republican.

The group also has a few favorite legislators, such as Republican Reps. Jonathan Stickland of Bedford, Matt Rinaldi of Irving and Tom Oliverson of Cypress.

In a video on the group's Facebook page, Oliverson, a physician who vaccinates his children, said the debate is not about the science but about parental rights.

"This issue is about liberty," he said in the video. "I do not want to live in a state where the state dictates to parents what medical decisions they must make on behalf of their children."

Texans for Vaccine Choice helped kill two bills during the 2017 legislative session that would have required schools to disclose their immunization rates on individual campuses. The group also successfully advocated for legislation that prevents courts or Child Protective Services from removing a child from a home on the grounds of vaccination status and measures that bar doctors from vaccinating new foster children.

Jackie Schlegel, the group's founder and executive director, said she'll have her eye on lawmakers next session. She will be ready to organize families — she says she has 6,500 members — if they believe their right to choose is at at risk.

"This is really a matter of who is best equipped to make these medical decisions for your children," Schlegel said. "Is it you or is it a government official behind a desk?"

Such rhetoric dims the hopes of experts such as Hotez, who want stronger legislation to prevent more widespread exemptions. He and others point to places such as California, which closed its nonmedical exemption loophole in 2015 after a measles outbreak that originated at Disneyland and sickened more than 100 people. Most of those infected hadn't been vaccinated, according to the CDC.

"It's a fundamental right of childhood to be protected against these diseases," Hotez said.

Davis said the growing political power of the "anti-vax movement" has made it more difficult to pass the measures health officials want.

"We didn't have a good session in terms of advancing the ball on getting kids vaccinated," she said. "I suspect we're basically going to have to play defense, at least for a while, and just try to stop the anti-vax initiatives."

Nemeczky, the Frisco mom, gave $59 to the PAC this summer. Her son's autism diagnosis changed her life and has led her to be more politically active.

She just wants parents to make their own choices about vaccinations.

"And I don't want anyone taking away my right to do the same."