Editor's Note: Officials said Denton County's number was incorrectly calculated when several schools counted the number of "shots not given" instead of the "students not vaccinated." County officials said they're recalculating and that the number is closer to 1.5 percent. See the most recent report here.

As kids head back to school, NBC 5 Investigates found three times as many parents are saying "no" to vaccines compared to just seven years ago and in some parts of the metroplex, the rate is even higher.



Parents like Tanya Garcia rushed to get their kids the shots Texas schools require. "I always got him vaccinated. I believe in it. I think it works," said Garcia.



But other moms like Jennifer Salas are saying "no" to vaccines.



"As a parent you have a choice and I think most parents don't realize that," said Salas.



Salas filled out a "conscientious exemption" form with the state – saying that she doesn't want her five-year-old son, Charlie, to have vaccines.



It's not that Salas is opposed to medicine because she's actually a nurse, but things she's read make her question if vaccines are safe enough.



Salas said people who work with her in the medical try to talk her out of skipping vaccines.



“They think I’m out of my mind crazy for doing it”, she said. “I say it’s my decision.”



And Salas is not alone.



In 2007 10,404 Texas parents opted out of at least one vaccine. By last year that number more than tripled to 32,616. That's still a fraction of the 27 million people living in Texas. But the rate of change has some doctors concerned especially in counties where the rate has risen even more dramatically.

In Collin County, 642 parents opted out in 2007. Last school year that number jumped to 2492, almost four times as many.



In Denton County, 401 parents opted out in 2007. Last school year that rose to 3692, nearly 10 times as many.



"Sadly most doctors, most people in public health, are not surprised the number of people opting out of vaccines is growing," said Dr. Seema Yasmin, a public health professor and health reporter at the Dallas Morning News.



"Sometimes the overall number of people who opt out of vaccines doesn't look big but what's disturbing is we get these hot spots where there's lots of people who've opted out of the vaccine and that's really concerning," said Yasmin.



In Denton County, 3.5 percent of students now skip at least one vaccine according to state stats, which leaves Denton County with the third highest rate of students skipping vaccines in the entire state.



Medical professionals say they're trying to pinpoint the reason more Denton County parents are saying no to vaccines.



Denton County Health Director, Matt Richardson, suspects some parents are persuaded more by things they hear from friends or read online than by doctors.



And then there's also the celebrity factor. Stars like Jenny McCarthy have spoken out raising questions about some vaccines, prompting more buzz among parents



McCarthy says she is not "anti-vaccine," but wants parents to have choices and drug companies to remove some vaccine ingredients.



"She had a great impact, a very large impact. She got my mind thinking about those options," said Salas.



Salas is convinced she's doing the right thing for her son who has a mild form of autism.



Even though The American Academy of Pediatrics and the CDC say there is no link between vaccines and autism, many parents still have questions.



Health officials say they need to work harder to persuade people that the benefits of vaccines outweigh the risk of disease.



"In these groups of unvaccinated children they are at risk, and then other children around them are at risk, and we're trying to combat that," said Richardson.



And with kids heading back to class some doctors worry about schools with more students skipping out on a shot in the arm.



"So if you think about a school classroom if one child doesn't have a vaccine it's unlikely other kids are going to get sick, but you start seeing 5 to 10 kids not getting that vaccine, suddenly you have a situation where there could be a deadly outbreak," said Yasmin.

It's not just the suburban counties where the numbers are up.



In Dallas County, twice as many parents are opting out compared to seven years ago and three times as many in Tarrant County.



The state made a few changes to the vaccine schedule during that time, including adding meningitis vaccines for 7th graders so that addition may also contribute to more parents saying no to at least some shots.

*The data in the graphs above are from the Annual Survey of Immunization Status; it is mailed to approximately 1,300 independent school districts (ISD) and 800 accredited private schools in Texas to collect the immunization status of children and the number of conscientious exemption affidavit forms filed at the private school and ISD level. The data is self reported and although the Annual Report of Immunization Status is mandated by law not all schools participate each year. The total district conscientious exemption data from the annual report is only reported at the district level so it includes all students from kindergarten through 12th grade. Please note that the total district conscientious exemptions are the number of students that have a conscientious exemption form on file at the school.