First Lyme Disease Vaccine in 20 Years Begins Final Clinical Trial—What You Need to Know

The vaccine, which likely won't be available for a few years, is slated to provide more protection against the tickborne disease.

Dangerous deer tick and small child legs in summer shoes on a grass
Photo: Getty Images

Fast Facts

  • A new Lyme disease vaccine, created by Pfizer and European drugmaker Valneva, has entered its final clinical trial.
  • 6,000 people in Europe and the U.S. will be participating in the trial to see if the shot can prevent Lyme disease, which is transmitted from tick bites.
  • The Lyme disease vaccine would be the first one available to the public in 20 years.

A new vaccine to prevent Lyme disease is entering the final phase of clinical trials, manufacturers Pfizer and Valneva announced last week. It would give Americans an extra layer of protection against the tickborne disease, which may cause as many as 476,000 illnesses each year.

The vaccine candidate, called VLA15, is being tested as four doses (three primary doses plus one booster dose) in humans and has had promising results so far. In the upcoming Phase 3 clinical trial, researchers will further investigate the efficacy and safety of the vaccine.

"With increasing global rates of Lyme disease, providing a new option for people to help protect themselves from the disease is more important than ever," Annaliesa Anderson, PhD, senior vice president and head of vaccine research and development at Pfizer said in a press release. "We hope that the data generated from the Phase 3 study will further support the positive evidence for VLA15."

Here's what we know about the new vaccine, how it works to protect against Lyme disease, and when shots might become available.

A Vaccine to Meet a Growing Need

Lyme disease is the most common vector-borne illness in the U.S., and is typically caused by the bacteria Borrelia burgdorferi. It's transmitted to humans through blacklegged ticks infected with the bacteria—and if you live in the U.S. or another region where it's endemic, you've likely heard of it.

"I think it's finally reached a point where it's something that a lot of people have heard of," Bobbi Pritt, MD, chair of the division of clinical microbiology at Mayo Clinic, told Health. "They're worried, they're concerned about Lyme disease, and so the time is right, and we certainly have the science to be able to create a Lyme disease vaccine."

If approved, VLA15 will be the only Lyme disease vaccine in the U.S., it won't be the first vaccine used to prevent the illness. Another vaccine, LYMERix, was used for a short time in the early 2000s, and reduced infections by nearly 80%. However, complaints of arthritis and other adverse effects from the vaccine decimated demand for LYMERix, and the FDA discontinued it in 2002.

In the two decades since, however, there's been a greater need for a vaccine. With climate change, humans are at a higher risk of coming into contact with ticks because of earlier springs and longer summers. Increasing populations of mice and deer, which carry the ticks, as well as humans spending time outdoors in places they weren't previously, may also be to blame for an increase in cases and risks, Dr. Pritt explained.

The new vaccine, VLA15, is a multivalent protein subunit vaccine, which works by targeting the outer surface protein A (OspA) of Borrelia burgdorferi.

"The protein that the vaccine targets is called OspA and this is a protein that's really really abundant on the bacteria," Dr. Pritt said. "If the body has already been exposed [to OspA] through a vaccine and generated a really strong immune response, then the body can fight off the bacterium as soon as it possibly even enters the body."

The multivalent aspect of the vaccine—which means it targets multiple proteins found on different strains of bacteria—also allows for more expansive coverage, according to a spokesperson for Pfizer.

"Our potential vaccine represents a potential improvement upon earlier vaccines by providing coverage for OspA serotype 1 that is found in North America," the Pfizer spokesperson told Health. "As well as serotypes 2 through 6, to provide coverage for the predominant Borrelia [bacteria] causing Lyme disease in Europe."

Approximately 6,000 participants ages 5 and older across 50 different sites where Lyme disease is endemic—including the U.S., Finland, Germany, the Netherlands, Poland, and Sweden—will be enrolled in the upcoming Phase 3 trial. Participants will receive a primary series of three vaccine or placebo doses, followed by a single booster vaccine or placebo dose.

When Could the Vaccine Be Available?

Though the VLA15 vaccine could be effective in helping those at risk for contracting Lyme disease both in the U.S. and in Europe, people may have to wait a few years before we see any shots in arms.

There's no official timeline for when data on VLA15 could be released, though the Pfizer spokesperson told Health that the study will last just shy of two and a half years. Based on this timeline, it may not be until 2025—when Pfizer could potentially submit for FDA approval—that we know whether the vaccine could become widely available.

"Our goal is to deliver a safe and effective vaccine to help protect those who may come into contact with infected ticks," the spokesperson added, "and possibly provide a solution to this growing unmet need."

With the public's distrust of the last Lyme disease vaccine, Dr. Pritt added, the clinical trial will surely be keeping an eye out for any specific side effects or dangers associated with it.

But years down the line, assuming the vaccine is effective and safe, Dr. Pritt said that she can see a world where the VLA15 shot is widely available for those who want it—especially if they spend time outdoors in the Upper Midwest and Upper Northeast or in parts of Europe, where the disease is highly endemic.

"I think it would be something available to at-risk populations, but not something that would be recommended for everyone," Dr. Pritt said. "For people that are outdoors a lot and potentially exposed to ticks—for example, people who like to hike and camp, or park rangers—those are people that would really benefit from getting the vaccine."

Relying on Prevention Strategies For Now

Until a Lyme disease vaccine becomes available, the best methods of prevention are avoiding wooded areas, using EPA-approved bug spray, and checking your body and clothing for ticks after being outside.

According to Dr. Pritt, about half of people who contract Lyme disease never even remember being bitten by a tick, so being on the lookout for symptoms is also crucial. This is especially true because, when caught early, Lyme disease is much more easily treated with antibiotics.

"The most common sign or symptom that they have is a rash at the site where they were bitten by that tick. It's called a bullseye rash because it looks a bit like a bullseye—it's red, it usually has a clear center, and it gets bigger over time," Dr. Pritt explained.

Not everybody will develop a hallmark bullseye rash, though, and it could be in some place where it isn't easily spotted, she added. In that case, keep an eye out for rashes, swollen lymph nodes, fatigue, and aches—these can all be an indication of an early Lyme disease infection.

Though VLA15 could certainly change the game when it comes to Lyme disease protection, those most basic prevention strategies are always there to rely on.

"I would just continue to stress the importance of tick bite prevention. So even if I was vaccinated, I would still wear bug spray. If I went outdoors, you know, like vaccines are good, but they're not 100% effective," Dr. Pritt said. "So you always want to just take those extra measures to help protect yourself."

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