Researchers are seeking thousands of volunteers in the U.S. and Europe to test the first potential vaccine against Lyme disease in 20 years in hopes of finding a better way to fight the tick-borne threat.
Lyme disease, caused by bacteria entering the body through the bite of an infected tick, is a growing problem, with reports of case numbers rising and warming weather helping ticks expand their habitat.
While a vaccine for dogs has long been available, the only Lyme disease vaccine for humans was pulled from the U.S. market in 2002 due to lack of demand, leaving people to rely on bug spray and tick checks.
"There's currently no Lyme disease vaccine available for humans," according to Health Canada. "However, there are clinical trials taking place in Europe and the U.S."
Those trials involve Pfizer and French biotech company Valneva. They are aiming to avoid previous pitfalls in developing a new vaccine to protect both adults and kids as young as five from the most common Lyme strains on two continents.
When the last vaccine was pulled from the market, Pfizer vaccine chief Annaliesa Anderson told the Associated Press that "there wasn't such a recognition, I think, of the severity of Lyme disease."
Robert Terwilliger, an avid hunter and hiker, was first in line Friday when the study opened in central Pennsylvania. He's seen lots of friends get Lyme and is tired of wondering if his next tick bite will make him sick.
"It's always a worry, you know? Especially when you're sitting in a tree stand hunting and you feel something crawling on you," said Terwilliger, 60, of Williamsburg, Pa. "You've got to be very, very cautious."
Canadian cases under-reported
Exactly how often Lyme disease strikes isn't clear.
The U.S. Centers for Disease Control and Prevention cites insurance records suggesting 476,000 people are treated for Lyme in the U.S. each year. Pfizer's Anderson put Europe's yearly infections at about 130,000.
In Canada, provincial public health units have reported 14,616 human cases of Lyme disease between 2009 and 2021. But the federal government says on its website the numbers are like under-reported "because some cases are undetected or unreported."
Black-legged ticks, also called deer ticks, carry bacteria that cause Lyme disease. The infection initially causes fatigue, fever and joint pain. Often — but not always — the first sign is a circular red rash around the spot of the tick bite.
Early antibiotic treatment is crucial, but it can be hard for people to tell if they have been bitten, since some ticks are as small as a pin.
Untreated Lyme disease can cause severe arthritis and damage the heart and nervous system. Some people have lingering symptoms even after treatment.
How the vaccine works
Most vaccines against other diseases work after people are exposed to a germ. The Lyme vaccine offers a different strategy — working a step earlier to block a tick bite from transmitting the infection, according to Dr. Gary Wormser, a Lyme expert at New York Medical College who isn't involved with the new research.
It does this by targeting an "outer surface protein" of the Lyme bacterium called OspA that's present in the tick's gut.
It's estimated a tick must feed on someone for about 36 hours before the bacteria spreads to its victim. That delay provides time for the antibodies the tick ingests from a vaccinated person's blood to attack the germs right at the source.
In small, early-stage studies, Pfizer and Valneva reported no safety problems and a good immune response.
The newest study will test the safety and efficacy of the new vaccine, called VLA15. The companies aim to recruit at least 6,000 people in Lyme-prone areas including the Northeast U.S. plus Finland, Germany, the Netherlands, Poland and Sweden.
Subjects will receive three shots of either the vaccine or a placebo between now and next spring's tick season. A year later, they'll get a single booster dose.
"We're really looking at something that's a seasonal vaccine," Anderson said, so people have high antibody levels during the months when ticks are most active.
Volunteers for the study can be as young as five and should be at high risk because they spend a lot of time in tick-infested areas, such as hikers, campers and hunters, said Dr. Alan Kivitz, who heads one of the study sites at Altoona Center for Clinical Research in Duncansville, Pa.
In his own practice, Kivitz said "not a single day goes by that someone either has a concern about Lyme disease, could possibly have Lyme disease."
Tick-bite prevention vaccine
The new Pfizer-Valneva vaccine is engineered somewhat differently than its predecessor and also targets six Lyme strains in the U.S. and Europe instead of just one.
The Pfizer study will span two tick seasons to get answers — but it's not the only research into new ways to prevent Lyme.
The University of Massachusetts scientists are working on a vaccine alternative, shots of pre-made Lyme-fighting antibodies. And Yale University researchers are in the early stages of designing a vaccine that recognizes a tick's saliva — which in animal testing sparked a skin reaction that made it harder for ticks to hang on and feed.
Since different tick species carry many diseases other than Lyme, ultimately "we're all hoping for a tick-bite prevention vaccine," Wormser said.