A prominent anti-vaccine activist is a scheduled headline speaker at a major natural health convention in Toronto this April – at a time when the World Health Organization is declaring vaccine hesitancy a top global health threat and two U.S. states battle measles outbreaks.

Del Bigtree, who produced an anti-vaccine film with Andrew Wakefield, a former doctor whose medical licence was stripped after he falsely claimed vaccines cause autism, will be at the Total Health Show to screen the movie and speak about what he describes as the risks of vaccines. The conference website says they expect 15,000 people to attend and they feature a number of prominent sponsors, including Newstalk 1010, Canadian Organic Growers and Healthy Planet, an official partner of the Toronto Raptors.

Health experts say they are concerned about the conference granting Mr. Bigtree a public forum and say the case illustrates how difficult it is to counter misleading, false information about health and medicine.

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“I’m very concerned about it,” said Natasha Crowcroft, chief of applied immunization research at Public Health Ontario. “Children are dying because of [anti-vaccination]. Adults are dying because of it. This is not a game.”

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In an interview, Mr. Bigtree said it’s important to be able to express competing views about vaccine safety.

“It was dangerous to speak out against the Third Reich,” he said. “Historically, we’re always told it’s dangerous to challenge the consensus view.”

When asked if he thinks vaccines are dangerous, Mr. Bigtree responded: “I know that vaccines are dangerous.”

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The Total Health Show, which has been running for more than 40 years, will be held April 12 to 14 at the Metro Toronto Convention Centre. According to the conference website, it’s North America’s premier natural health show and will feature 60 speakers and more than 200 exhibitors. It’s being held by a group called the Consumer Health Organization.

The conference features a number of other controversial speakers, including Toronto doctor Zoltan Rona, who suggested on Twitter this week the HPV vaccine causes cancer. He is scheduled to speak about the “horrors” of prescription drugs aimed at children. The conference website says Heather Fraser, board member of anti-vaccine group Vaccine Choice Canada, will speak about what she describes as the risks of vaccines and how “more parents are turning away from the procedure." Another speaker is a California naturopath who claims prescription drugs and poor nutrition are the underlying causes of gun violence. Dr. Rona and Ms. Fraser did not respond to a request for comment.

The conference organizers declined an interview request, but said in an e-mail statement that they “provide an open forum for the intelligent consumer to access, discuss and debate information on the varied options available for natural health, in order to make their own health decisions.”

Vinita Dubey, associate medical officer of health with Toronto Public Health, said the contentious views being presented at this conference represent a larger problem facing public health officials, as more people are bombarded with misleading information online.

“The misinformation of immunization information is a big public health problem,” she said. “It’s still up to the individual to make their choices."

Tim Caulfield, Canada Research Chair in health law and policy at the University of Alberta and critic of pseudo-science, said these types of conferences are problematic because they give legitimacy to people who are promoting views that can endanger public health.

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“Being exposed to this information does have an impact on attitudes,” he said. “It may seem trivial and it may seem like a small percentage of the population is anti-vaxxer, but the problem is this invites this broader attitude of doubt.”

Bell Media, parent company of NewsTalk 1010, Canadian Organic Growers and Healthy Planet did not respond to a request for comment in time for publication.