Generally, a child must be vaccinated in order to attend school.

But more and more people are sighting religious, medical, or philosophical beliefs in order to get their children out of being vaccinated.

Chantal Wilford's three kids are different than most children.

They haven't received all their vaccines. "Their health is extremely important to me and that's why I've done so much research into vaccines."

Madigan and Liam only received one vaccine, and her youngest, Callum, had none.

Chantal feared the vaccines could harm her children's immune systems and says her kids' chances of getting one of the diseases were slim.

"They are really very rare, and in most cases, the child can recover fully."

Chantal got a religious exemption so her kids can go to school.

She's not alone, the rates of opt-out requests have doubled in areas across the country.

"If you aren't vaccinating your child, you are making a mistake and putting them at risk for having a serious illness" says Pediatrician Mike Jordan.

He is concerned about the growing number of parents opting out.

He says many diseases that kids are vaccinated for are rare because of vaccinations.

"It's estimated, for instance, that if we stopped vaccinating against measles, there would be about 2.7 million deaths per year as a result of that."

In 1983, a child from birth to age six received 10 vaccines.

Today, the CDC recommends up to 36 vaccines to protect against 15 diseases -- everything from polio to the flu.

"Any time you see where there's a drop in people getting vaccinations, you start seeing a reemergence of the illnesses we are trying to prevent."

Although some parents fear vaccines can cause autism, Dr. Jordan says study after study has shown otherwise.

"There are some adverse reactions that are associated with certain vaccines. Autism is not one of them."

Chantal says "I think that the vaccines at the age that they get them are an assault on the immune system."

Instead, she chooses to give her children an organic diet and takes steps to build their immune systems without vaccinations.

All 50 states have vaccination exemption laws, but parameters differ by state.

Some only offer medical and religious, while other states offer philosophical exemption.

However, Chantal says she didn't have to prove her religious beliefs and no one asked her any questions about her religion.

Adverse effects of vaccines may include fever or allergic reactions, but doctor Jordan says they are rare.