Major test of 1st potential Lyme disease vaccine in 20 years begins in U.S., Europe

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."

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.