Seeking vaccine against Lyme disease, Pfizer and French partner Valneva launch major trial

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

If proven safe and effective, the vaccine, currently called VLA15, could be an important tool to stop 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 from lingering symptoms.

The first signs of a dangerous tick bite can include a bull's-eye rash, fatigue, fever, headache, muscle pain and a stiff neck. Without appropriate treatment, Lyme can cause arthritis, heart conditions and affect the nervous system.

An earlier Lyme vaccine, LYMErix, was taken off the market in 2002 after concerns about its safety, never proven, drove down interest and its manufacturer, GlaxoSmithKline, withdrew it.

This trial, with French company Valneva, will enroll about 6,000 volunteers, ages 5 and up at as many as 50 sites in a handful of countries where Lyme is a problem, including the United States.

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

The vaccine targets the outer surface protein of the Borrelia burgdorferi bacteria that causes Lyme disease. Blocking this protein apparently inhibits the bacteria's ability to jump from tick to person.

WATCH: Lyme disease is on the rise: What to do if you get a tick bite

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

In earlier trials in both labs and people, the vaccine "demonstrated a strong immune response and satisfactory safety profile," the companies said.

Assuming this Phase 3 trial goes well, the companies would likely submit a request for approval from the Food and Drug Administration in 2025.

“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, Pfizer's senior vice president and head of vaccine research & development, said in a statement. “We hope that 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 Monday's trial start. The companies have been collaborating to co-develop the vaccine since April 2020.

Contact Karen Weintraub at

This article originally appeared on USA TODAY: Pfizer launches Lyme disease vaccine trial with French partner Valneva