A Lyme disease vaccine may finally be on the way. Why did it take so long?

Ixodes tick on green grass with human silhouette representing exposure to infection. Vera D - stock.adobe.com Vera D - stock.adobe.com

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In 2009, there were only 144 reported human cases of Lyme disease in Canada. According to the most recent Public Health Agency of Canada (PHAC) data, there were 5,809 reported cases in 2024, and the preliminary number of cases for 2025 is 7,105. There’s no denying Lyme disease is on the rise.

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Caused by the bacterium Borrelia burgdorferi and spread through the bite of infected blacklegged ticks, the disease can cause fatigue, rash, fever, chills and muscle aches, among other symptoms. If left untreated, the infection can spread to joints, the heart and the nervous system.

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Previously, a vaccine called LYMErix was administered to prevent Lyme disease. It was approved by the FDA in 1998, but withdrawn from the market just three years later, following reports of adverse reactions causing a lack of demand. Now, Lyme disease is treated with a course of antibiotics.

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But Lyme disease vaccines for dogs have been available for years, so why isn’t there one for humans?

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Is there a Lyme disease vaccine for humans?

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No, there currently is no Lyme disease vaccine for humans. LYMErix was shelved in 2002, and there have been no new Lyme disease vaccines approved since.

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However, the pharmaceutical company Pfizer and French biotech firm Valneva are currently working together to develop a new vaccine, PF-07307405. As of March 2026, it has completed Phase 3 clinical trials.

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And Moderna is working on two more potential Lyme disease vaccines, called mRNA-1975 and mRNA-1982. These vaccines are not as far along in development as PF-07307405, and are both currently in Phase 2 clinical trials.

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This graph shows the rise of ticks in Canada, and the rate of their population spreading across the provinces from 1977 to 2024.

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What do we know about the Pfizer and Valneva vaccine?

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In March 2026, Pfizer and Valneva announced results from Phase 3 clinical trials of the Lyme disease vaccine they are co-developing.

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It demonstrated more than 70 per cent efficacy in preventing Lyme disease in individuals aged five years and above after four doses, with Pfizer now planning submissions to regulatory authorities.

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Annaliesa Anderson, senior vice president and chief vaccines officer at Pfizer, said in a news release that the result is “highly encouraging” and “creates confidence in the vaccine’s potential to protect against this disease that can be debilitating.”

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PF-07307405 works by causing a vaccinated person to create antibodies that are ingested by ticks when they bite them. These antibodies then inhibit the bacterium’s ability to leave the tick, preventing it from being transmitted to the human host.

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Blacklegged ticks are often found in wooded and forested areas, especially areas with thick underbrush. Photo by Getty Images

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Dr. Isaac Bogoch, a professor at the University of Toronto in the Department of Medicine and an infectious diseases specialist, tells National Post that while a Lyme disease vaccine is “definitely needed,” the positive results from the Pfizer-Valneva aren’t a sure indicator of success just yet.

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“It’s already three doses and a booster, so let’s just call it four doses,” he says. “The more doses, the more challenges you’re going to have with uptake and adherence. And if there are annual doses, and if it’s expensive and inconvenient, I think that’s going to limit the uptake.”