Pfizer and a French partner are launching a large clinical trial of an experimental Vaccine that would be the only one to prevent Lyme Disease, the companies announced on Monday.

If proven safe and effective, the vaccine, currently called VLA15, could be an important tool in stopping the tick-borne disease that affects nearly half a million Americans a year. Although many people clear the infection with a course of antibiotics, others suffer for years with persistent symptoms.

Early signs of a dangerous tick bite can include a rash, fatigue, fever, headache, muscle aches, and stiff neck. Without proper treatment, Lyme can cause arthritis, heart problems and affect the nervous system.

An earlier Lyme Disease Vaccine, LYMErix, was pulled from the market in 2002 after concerns about its unproven safety waned public interest and its manufacturer, GlaxoSmithKline, withdrew it.

The trial, with French company Valneva, will recruit around 6,000 volunteers, aged 5 and over, at no less than 50 sites in a handful of countries where Lyme is a problem, including the United States.

VLA15 is administered in three primary doses followed by a booster. Half of the volunteers will receive a saline placebo for the first three doses and the other half will receive a saline placebo as a booster, the company said.

The vaccine targets the outer surface protein of the bacterium Borrelia burgdorferi that causes Lyme disease. Blocking this protein apparently inhibits the bacteria’s ability to jump between ticks.

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The vaccine protects against six forms of the protein expressed by bacterial species found in North America and Europe.

In previous laboratory and human trials, the vaccine “demonstrated a strong immune response and a satisfactory safety profile,” the companies said.

Assuming this phase 3 trial goes well, the companies would likely submit an application for approval to the Food and Drug Administration in 2025.

“With rising global rates of Lyme disease, it’s more important than ever to give people a new option to protect themselves against the disease,” said Annaliesa Anderson, Pfizer senior vice president and chief vaccine research and development, in a statement. “We hope the data generated from the Phase 3 study will further support the positive evidence for VLA15 to date.”

Pfizer agreed to make a $25 million milestone payment to Valneva with the start of the trial on Monday. The companies have been collaborating to co-develop the vaccine since April 2020.

Contact Karen Weintraub at [email protected].