Large Lyme Disease Vaccine Clinical Trial Begins in U.S. and Europe

If approved, it would be the first new shot to combat the misunderstood disease in the U.S. in 20 years

A tick
A tick runs over a human hand. Getty Images

Tick-borne Lyme disease—long a source of stress for hikers and outdoorsy types—may soon become less of a threat. A new Lyme vaccine is under development, and this week, its creators announced the start of a large-scale clinical trial.

Health care providers report around 30,000 cases of Lyme to the Centers for Disease Control and Prevention each year, but the agency estimates the total is much greater—around 476,000 people in the U.S. annually.

Lyme disease is caused by bites from blacklegged ticks, more commonly known as deer ticks. The insects typically need to be attached for 36 to 48 hours to transmit the bacterium that causes infection, says the CDC. Symptoms include fever, headache, fatigue and—for 70 to 80 percent of infected people—a rash around the bite that expands over time and sometimes looks like a bull’s-eye.

The illness can be treated with antibiotics. If left untreated, though, Lyme can cause longer-lasting health problems, such as severe arthritis and damage to the heart and nervous system, report Lauran Neergaard and Shelby Lum of the Associated Press.

Lyme disease cases have been on the rise over the last couple of decades, wrote Knowable Magazine’s Ula Chrobak in February. Scientists think this trend could arise from several factors including rising temperatures, which speed up the tick life cycle and expand the range where ticks can survive. Additionally, researchers hypothesize that fragmentation of forests is also to blame, as humans build homes or malls beside smaller chunks of trees that host higher densities of ticks.

In small, early-stage studies, the vaccine revealed no safety issues and created a good immune response, reports the AP. Now, the next stage will further test the vaccine’s safety and ability to protect against disease.

The vaccine’s developers, Pfizer and the French pharmaceutical company Valneva, plan to enroll around 6,000 people over the age of 5 who live in the United States or Europe, according to Gizmodo’s Ed Cara.

If the trial is successful, the companies could seek official approval for the vaccine in 2025, writes NPR’s Bill Chappell. This would make it the only Lyme disease vaccine available in the U.S.

An earlier Lyme vaccine, approved by the U.S. Food and Drug Administration in 1998, was pulled in 2002 by manufacturers due to low demand. At the time, “there wasn’t such a recognition, I think, of the severity of Lyme disease” and how many people it affects, Pfizer vaccine chief Annaliesa Anderson tells the AP.

While most vaccines against other diseases kick in after people have been exposed to a germ, the Lyme vaccine candidate stops the tick bite from transmitting the infection to begin with, Gary Wormser, a Lyme expert at New York Medical College who isn’t involved with the clinical trial, tells the AP.

Other researchers are also currently working on an antibody treatment for Lyme, with the first phase of human trials expected to end this month, according to NPR. And scientists at Yale University are developing a tick bite vaccine, which would protect against tick-borne illnesses in general, including Lyme, Gizmodo reports.

“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,” Anderson said in a statement released Monday.

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