-- Former "The Hills" star Kristin Cavallari recently told Fox Business that she didn't vaccinate her son Camden, 1, and would not be vaccinating her second son that she's expecting later this year because she fears of the side effects of vaccines, especially autism.
Bravo's Andy Cohen asked her to explain that controversial stance last night on "Watch What Happens Live."
"Here's the thing," the 27-year-old reality TV star said. "At the end of the day, I'm just a mom, I'm trying to make the best decision for my kid."
She added, "There are very scary statistics out there regarding what is in vaccines and what they cause -- asthma, allergies, ear infections, all kinds of things. We feel like we are making the best decision for our kids."
She added that it was a personal decision and implied that she's not telling other parents to do the same.
The U.S. Centers for Disease Control and Prevention and the Institute of Medicine concluded in 2004 that there is no link between vaccines and autism upon examining the medical and scientific studies on the matter. They debunked the small 1998 study that originally suggested the link and set off a panic.
The most common vaccine side effects are a low grade fever and a sore arm, according to the CDC. Though more serious allergic reactions to vaccines have occurred, they're extremely rare -- often too rare to calculate, according to the CDC.
Learn about reactions to specific vaccines here.
Communities in which large numbers of people have not been vaccinated have seen resurgences of preventable diseases, such as whooping cough and the measles. For instance, a Texas mega-church was blamed last summer for a measles outbreak that sickened 20 people after investigators learned that the church's founder told congregants that vaccines may cause autism.