Open this photo in gallery The billboards are in a number of locations around the city, including outside of Toronto’s Eaton Centre (pictured). J.P. MOCZULSKI/The Globe and Mail

An anti-vaccine group has placed dozens of billboards in the Greater Toronto Area suggesting vaccines are risky and that children don’t need immunizations to attend school, a sign of the challenge facing public-health officials at a time when cases of measles are on the rise.

The group, Vaccine Choice Canada, has four different images rotating on 50 digital billboards in Toronto and the surrounding area, according to the Facebook page of Ted Kuntz, the group’s vice-president. The billboards are in a number of locations around the city, including outside of Toronto’s Eaton Centre. Mr. Kuntz wrote that the advertising campaign, which began last week, will run for two weeks and will generate at least two million impressions. In the Facebook post, Mr. Kuntz thanked numerous donors who made the billboard campaign possible.

Vinita Dubey, associate medical officer of health with Toronto Public Health, said the campaign is concerning and should prompt a discussion about banning advertisements that promote false or misleading messages.

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“There is legislation available to prevent tobacco companies from advertising,” Dr. Dubey said. “There is some precedent for being more legislative and proactive about messaging."

The World Health Organization has declared vaccine hesitancy, or the refusal or reluctance to be vaccinated, as a top health threat in 2019. B.C. is dealing with a measles outbreak that has so far infected 13 people. Around the world, measles cases and deaths are on the rise and in many countries, it’s linked to falling vaccination rates.

Dr. Dubey said the billboards use “half-truths” to lure people in.

“They play on a truth that you may know, but they don’t quite give you the full story. That’s what gives you the seed of doubt and makes you question," she said.

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Natasha Crowcroft, chief of applied immunization research at Public Health Ontario, said the billboards were clearly designed so the casual observer wouldn’t know they were created by an anti-vaccine group. “It’s really poisonous in a really subtle way,” she said.

Vaccine Choice Canada declined an interview request. In an e-mail, Mr. Kuntz said the aim of the campaign is to encourage people to become more educated about vaccines. He did not respond to questions about the group’s funding.

Outfront Media, the advertising company that is running the billboards, did not respond to numerous requests for comment.

The risks associated with vaccines are low and the majority are not serious. According to Public Health Ontario’s most recent vaccine safety report, there were 8.5 million publicly funded vaccine doses given in Ontario in 2017. Of those, there were 696 adverse event reports, which included 279 sore arms, 159 rashes and 120 allergic skin reactions. There were 26 serious adverse events, which translate to three for every one million vaccine doses given to people. The serious events included severe vomiting and diarrhea; Kawasaki disease, which causes high fever and can lead to heart damage if left untreated; as well as an infected abscess and a case of aseptic meningitis.

The risks of vaccine-preventable diseases are much higher. For instance, one in every 1,000 people with measles will develop encephalitis, or inflammation of the brain that could cause permanent damage, according to the BC Centre for Disease Control. One in every 3,000 people with measles will die from respiratory or neurologic complications.

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Dr. Crowcroft said balancing the small risks of vaccines with the much larger chance of suffering through an illness and the potential complications comes down to basic math.

“The problems associated with the disease are so much more common that nobody in their right minds would say ‘I don’t want the vaccine, I’d rather my kid have diphtheria,'" she said.