A new Lyme disease vaccine, developed by Pfizer and European pharmaceutical company Valneva, has entered its final phase of clinical trials. If successful, it would be the first publicly available Lyme disease vaccine in over two decades and could offer much-needed protection against the tick-borne illness that affects hundreds of thousands of people annually in the U.S.

The vaccine, known as VLA15, is being tested as a four-dose series—three initial doses followed by one booster. Previous phases have shown encouraging results, and the current Phase 3 trial will further evaluate the vaccine's safety and effectiveness.

“With the growing prevalence of Lyme disease globally, having a new preventive option is more important than ever,” said Annaliesa Anderson, PhD, Senior Vice President and Head of Vaccine R&D at Pfizer. “We hope the data from this Phase 3 study will support the promising evidence we’ve seen so far.”

Why a Lyme Vaccine Is Needed Now

Lyme disease is the most common vector-borne illness in the U.S., caused by the bacterium Borrelia burgdorferi. It’s transmitted to humans through the bite of infected blacklegged ticks. Increased awareness, rising case numbers, and environmental changes have all contributed to the urgency of a new vaccine.

“Lyme disease has become a widely recognized concern, especially in regions where it’s endemic,” said Dr. Bobbi Pritt, Chair of Clinical Microbiology at Mayo Clinic. “With the science available today, this is the right time to bring a Lyme vaccine back.”

The U.S. had a Lyme disease vaccine once before—LYMERix, which was introduced in the early 2000s and showed up to 80% effectiveness. However, concerns about potential side effects, including arthritis, led to a decline in public trust and ultimately its withdrawal from the market in 2002.

Since then, climate change has expanded the range of ticks, and increasing populations of animals like deer and mice—natural hosts for ticks—have heightened the risk. Humans are also spending more time in outdoor areas where ticks thrive.

How the Vaccine Works

VLA15 is a multivalent protein subunit vaccine designed to trigger the immune system to fight Borrelia burgdorferi by targeting OspA—a protein found on the outer surface of the bacteria.

“The OspA protein is highly expressed by the bacterium, and by exposing the body to this protein in the vaccine, we hope to train the immune system to quickly eliminate the bacteria if infection occurs,” explained Dr. Pritt.

The vaccine’s multivalent design means it offers coverage against multiple strains of Borrelia, including those found in North America and Europe. According to Pfizer, it targets OspA serotype 1 (common in the U.S.) and serotypes 2 through 6 (found in Europe).

Trial Details and Who Will Be Vaccinated

The Phase 3 trial will enroll around 6,000 participants aged 5 and older across 50 sites in the U.S., Finland, Germany, the Netherlands, Poland, and Sweden—regions where Lyme disease is endemic. Participants will receive either the vaccine or a placebo in a three-dose series, followed by a booster dose.

When Could the Vaccine Be Available?

Although the vaccine shows promise, it will be at least a few years before it becomes publicly available. The trial is expected to last just under two and a half years, meaning data may not be ready until 2025. At that point, Pfizer could potentially seek FDA approval.

“Our objective is to deliver a safe, effective vaccine for those at risk of exposure to infected ticks and address this growing health need,” a Pfizer spokesperson said.

Given the historical skepticism around Lyme vaccines, researchers will pay close attention to potential side effects during the trial. Still, if the vaccine proves both safe and effective, experts anticipate it could become a valuable tool—particularly for people who spend a lot of time outdoors in tick-prone regions like the Upper Midwest and Northeast U.S., or parts of Europe.

“I see this vaccine being recommended for those at higher risk—campers, hikers, park rangers—not the general population,” said Dr. Pritt.

What To Do Until Then: Prevention Still Matters

Until the vaccine becomes available, tick prevention remains essential. Key strategies include:

• Avoid wooded or grassy areas where ticks live

• Use insect repellents approved by the EPA

• Wear long sleeves and pants when outdoors

• Check your skin, clothing, and pets after spending time outside

Because many people never notice a tick bite, it’s also important to watch for symptoms like the classic bull’s-eye rash, swollen lymph nodes, fatigue, and body aches. These could be early signs of Lyme disease—and early treatment is most effective.

“Even if I were vaccinated, I would still use insect repellent,” said Dr. Pritt. “Vaccines help, but no method is perfect, so you should still take every precaution possible.”