The opt-out policy is legal if you follow the guidelines required by the state of Texas. But it's controversial because someone else's decision to opt their child out might affect your newborn baby when you come into contact with them at the grocery store.
Alma Anchondo brought makes it a point to keep her daughter's vaccinations up to date. And she is surprised that some parents opt out of the required school vaccinations.
"I think it's not OK for other kids to go to school without shots," Anchondo said.
In the 2012-2013 school year, the Centers for Disease Control and Prevention found that the parents of 7,000 Texas kindergarten children opted out of vaccinations. And that worries public health officials here in Houston.
"Today's parents haven't seen those epidemics and they don't know the risks they're putting their child in by not vaccinating them," said Dr. Catherine Troisi with the UT School of Public Health.
Troisi says the children at risk are not only the ones who aren't vaccinated, but babies who are too young to get their vaccinations. It's also a risk for children with cancer and AIDS who can't get vaccines for medical reasons.
"It's estimated that for every person who has measles, that person infects another 12 to 15 people," Troisi said.
She says parents opt out because they worry about a young child getting so many vaccines at the same time.
"When parents are afraid -- they're trying to do the best for their kids and so are we -- and there's a lot of scary stuff out there on the Internet and a lot of misinformation," UTHealth pediatrician Dr. Kim Connelly said.
Much of that misinformation involves claims made by a British doctor, who has since lost his license, that the measles vaccine can cause autism. The claim has since been refuted. But it's contributed to a 1 percent opt out rate for philosophical reasons in Texas last year.
"Some areas like Colorado I think has a much higher rate of people who don't immunize for philosophical objections and they do have more outbreaks," Connelly said.
"I don't think anyone wants to go back to a 1930s, 1940s world where so many children died of these diseases," Troisi said.
For families who opt out, the CDC says it's important to tell your pediatrician and any other medical people that may take care of him. If there's an outbreak of a vaccine preventable disease in your area, the CDC says parents should be prepared to keep their children at home until the school says it's safe for them to return.
The CDC also recommends these parents be especially careful when traveling so the unvaccinated child isn't exposed to and doesn't expose others to vaccine-preventable diseases.