This story was originally published on April 12, 2019.

Reading horror stories online about parents claiming their kids were "never the same" after being vaccinated convinced Kristen O'Meara to keep her three children unvaccinated.

Longstanding scientific evidence — backed by the World Health Organization, Centers for Disease Control and Prevention and Health Canada — show that vaccines are proven to be safe, and there is no link between receiving vaccines and developing serious or chronic illnesses. But that didn't quell O'Meara's skepticism when it came to deciding whether to vaccinate her children.

In O'Meara's case, the information she read from alternative online sources ultimately pushed her to decide to skip out on vaccinating her kids.

"[If] I vaccinate them, and they have some horrible reaction, I will feel guilty for the rest of my life," O'Meara told Out in the Open host Piya Chattopadhyay of her former mindset.

Myths and conspiracy theories trying to disprove the need for vaccines continue to thrive. The World Health Organization now lists "vaccine hesitancy" among its Top 10 threats to global health in 2019.

Dr. Paul Offit, an American pediatrician specializing in infectious diseases and the co-inventor of the rotavirus vaccine, says that because these kinds of diseases aren't as prevalent anymore, people aren't afraid, or as compelled to take preventative measures.

Your choice not to get a vaccine is not a risk-free choice. - Dr. Paul Offit, American pediatrican

"If you're worried about a vaccine, and you were hoping that maybe there's a reason for not getting it, you can easily find those reasons on the internet, even though they're not science-based and accurate," Offit told Out in the Open.

He also points out that as a society, we're more prone to conspiracy theories, and says there's a belief that "pharmaceutical companies are dark, or that they're controlling the medical establishment." A recent survey by Insights West suggested similarly with 20 per cent of B.C. residents who responded believing vaccinations are encouraged so pharmaceutical companies can make money. B.C. is grappling with a recent measles outbreak.

Catching rotavirus

When a measles outbreak that originated at Disneyland in California in 2015 spread to O'Meara's hometown of Chicago, she remained convinced that vaccinations were unnecessary because she felt that the chances of being infected were slim to none.

But her viewpoint quickly changed when all her children caught rotavirus, a contagious virus that causes fever, vomiting and diarrhea. She, along with her kids, were severely sick for days.

"I kind of had a moment of reckoning where I was like, 'Oh my gosh, that was rotavirus — there's a vaccine for that,'" she said.

Kristen O'Meara and her three children live in Chicago. (Submitted by Kristen O'Meara)

O'Meara felt immense guilt knowing that her kids became ill as a result of her decision not to vaccinate them. But the urgency to get them vaccinated didn't come until a respected colleague shamed her after hearing what had happened.

"She looked at me dead in the eyes and just said, 'Now that makes me angry,'" O'Meara said of the exchange with her peer.

It was the first time O'Meara said she'd been confronted so directly about her decision. After that conversation, she finally made the choice to vaccinate her three children.

'Not a risk-free choice'

O'Meara said that having someone that she respected criticize her was much more influential than getting information from an online source or TV.

"You come to your truth when you come to it. Hopefully for most parents, it's sooner than I did," O'Meara reflected.

B.C. provincial health officer Dr. Bonnie Henry and CBC reporter Bethany Lindsay address five misconceptions about the vaccine for measles, mumps and rubella. 2:49

In regards to prevention, Dr. Offit believes that it's everyone's responsibility to educate parents on the risks of not vaccinating their children — including health-care officials, doctors and journalists.

"Your choice not to get a vaccine is not a risk-free choice. Measles can kill you. I think we need to be more compelling, passionate and compassionate in our storytelling — make sure people understand what's at stake here."

With files from CBC News. This story appears in the Out in the Open episode "Switching Sides".