London man among thousands who've rolled up their sleeves to trial Lyme disease vaccine

Working outdoors as a landscaper in the summer, Maxwell Dick is at a higher risk than most people of being bitten by a tick and developing a tick-borne disease.

The most prevalent of them, and the most common vector-borne disease in North America, is Lyme disease, which has seen case rates soar over the past decade. Despite that, and the potentially debilitating long-term symptoms that can result, including chronic fatigue, body aches and cognition issues, no preventable vaccine is currently available.

"There's a lot of people in my industry who get ticks all the time, and to prevent some Lyme disease would be wonderful," Dick said.

With that in mind, the London resident and Fanshawe College horticulture instructor signed up for a clinical study for a new, potential Lyme disease vaccine.

The clinical trial for the vaccine, VLA15, developed by Pfizer and Valneva, began in August 2022. Stage 3 trials got underway in late 2023 involving more than 9,000 participants from areas of Canada, Europe, and the U.S. where the disease is endemic.

Dick says he signed up after seeing a form at his doctor's encouraging participants. "It literally was like, 'Are you a landscaper? Do you like being outdoors? Do you hike? Do you have pets?' I was like, yes to everything," he said.

Half of the participants receive three doses of VLA15, while the other half receive three doses of a placebo, both within the first year, followed by a booster a year later. Dick says he expects to find out what he was given in December or January.

"They called me (April 14) because I had gotten my blood taken for the last time a few weeks ago, and they were just checking in … It's funny, they're like, 'we don't want you to get a tick, but if you do, that'd be great,'" he said with a chuckle.

Pfizer and Valneva say they expect Stage 3 to finish by years-end, and in July said the vaccine had "shown a favourable safety profile across all dose and age groups" in all trials to date.

CBC News has reached out to Pfizer for comment.

Should the vaccine go to market, it would be the first in more than 20 years. LYMErix, a vaccine from SmithKline Beecham, now GSK plc, was approved in the late 1990s but pulled by the drugmaker in 2002.

In 2018, Sam Telford of the original research team blamed the decision on low sales revenue and a class action lawsuit alleging significant adverse reactions. The suit was settled in 2003, with no financial compensation awarded to claimants.

The new vaccine is similar in that it also targets the same surface protein (OspA) of the spirochete bacterium that causes Lyme disease, said Dr. George Chaconas of the University of Calgary. There are some differences.

"If you get the vaccine, your body develops antibodies to OspA. When the tick takes a blood meal, along with the blood come your antibodies," which kill the bacteria while they're in the tick, he said. "The mechanism is quite cool."

Chaconas's research focuses on Borrelia burgdorferi, the bacterium spread through the bite of an infected tick. A tick needs to be attached for at least 24 hours to transmit the bacteria, Health Canada says.

Lyme disease is treated with antibiotics, but some may experience post-treatment Lyme disease syndrome, or PTLDS, which is believed to be an autoimmune response, he said.

"You don't want to get PTLDS or even Lyme, for that matter. Taking precautions when you're out where you might encounter ticks is important."

Cases of Lyme disease continue to climb in Canada, rising in the last decade from 522 in 2014 to 5,229 in 2024, Health Canada says.

Infectious disease experts attribute rising awareness among the public and health officials and the warming environment, which is pushing ticks further north. Most major centres in Ontario are established risk areas.

"The tick boundary is not static. If you have shorter winters and winters that aren't as cold, ticks can survive and thrive in more northern latitudes," said Dr. Isaac Bogoch, an infectious disease specialist at Toronto General Hospital.

It raises concerns about other tick-borne diseases, such as anaplasmosis, babesiosis, and Powassan virus, which were designated tick-borne diseases of public health significance in Ontario in 2023.

Lyme disease gets more attention, "as it should," Bogoch says, "but we shouldn't ignore the other ones."

Case figures of the diseases are likely significant undercounts, he said. Many may not recognize signs and symptoms, or seek out medical attention.

"They're not hard to diagnose, and they're not hard to treat. This is just an issue of being aware that they're around and identifying them," he said.

Increasing tick surveillance, identifying changing geographic boundaries of tick-related disease, and improving education and communication are key to addressing tick-borne disease, he says.