The participants will get three doses of the vaccine, called VLA15, or a placebo, followed by a booster dose.
“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, senior vice president and head of vaccine research and development at Pfizer, said in the news release .
VLA15 is the only Lyme vaccine in clinical development, Pfizer said in the statement. It targets the bacteria Borrelia burdorferi, the main cause of the tick-borne disease, and has “demonstrated a strong immune response and unsatisfactory safety profile in pre-clinical and clinical studies so far.”
If the trial shows that the vaccine is safe and effective, Pfizer says, it could submit requests for approval from the US Food and Drug Administration and the European Medicines Agency in 2025.
What is Lyme disease?
Lyme disease is the most common vector-borne disease in the US, according to the US Centers for Disease Control and Prevention, and it’s becoming common in more areas.
An estimated 476,000 Americans are diagnosed and treated for Lyme disease each year, although the CDC says this is probably an overcount because people are sometimes treated without official confirmation that they have the disease.
The only vaccine previously marketed in the US was discontinued in 2002.
Lyme disease symptoms
Fever, chills, body aches, swollen lymph nodes, neck stiffness, shortness of breath, headache, fatigue and a rash are all typical symptoms of Lyme disease.
When you get bit by a tick, you will typically see a small red bump that may look like a mosquito bite. But three to 30 days later, if a rash shows up and expands from that red area and looks a little like a bull’s-eye, that’s a sign you may have Lyme disease.
Doctors will call this rash erythema migrans. Often, it will expand slowly. It’s not normally itchy or painful, but the area may feel a little warm when you touch it.
Between 70% and 80% of people with Lyme disease develop this rash, and some get it at more than one place on their bodies.
Left untreated, the infection can spread to the joints, heart and nervous system, according to the CDC. This can lead to joint pain and swelling.
After several weeks to months, there may also be swelling of the membranes surrounding the brain, temporary paralysis of one side of the face and “brain fog”: forgetfulness or confusion.
How people get Lyme disease
Most commonly, blacklegged ticks, also known as deer ticks, carry Lyme disease. They live in the northeastern US, Midatlantic and upper Midwest. The Lyme disease-carrying Western blacklegged tick can be found along the Pacific coast.
Most people get sick with Lyme disease in the spring and summer months. That’s when the immature ticks called nymphs are most actively feeding, and that’s when most people are out and about, walking through grass and the heavily wooded areas where the bugs like to hang out.
What to do if you get bitten
Ticks can be tiny: Deer ticks may be as small as the head of a pin, so look for them carefully.
Removing a tick within 24 hours cuts your risk of developing Lyme disease. The longer the tick is attached to the body, the more likely that person will be infected. Use tweezers to carefully and steadily pull the tick off, grasping near its mouth or neck. Then put antiseptic on the infected area.
If you’ve been bitten and develop symptoms, call your doctor immediately. Even if your symptoms disappear, you should still see a doctor.
Lyme disease treatment
The standard treatment for Lyme disease in early stages is oral antibiotics. Usually, a 14- to 21-day course is recommended, but some studies suggest that a 10- to 14-day course is equally effective, according to the Mayo Clinic.
If the central nervous system has been affected by the disease, intravenous antibiotics may be given for 14 to 28 days. This treatment eliminates the infection, but you may need more time to recover from symptoms. The side effects from this treatment may include a lower white blood cell count, diarrhea or infection with other organisms resistant to antibiotics that are unrelated to Lyme disease.
People who are put on antibiotics early in the disease generally make a full recovery, according to the Mayo Clinic. It may take patients who get treated later in the infection longer to respond to treatment.
The CDC recommends wearing insect repellent with at least 20% DEET concentration and avoiding wooded areas with high grass, where ticks are most often found.
Check for ticks daily and, if you spend a lot of time outdoors, take frequent showers. The washcloth can help remove unattached ticks.
When you are outside, cover up. Wear long sleeves, long pants and hats when walking or hiking in the woods.
Your dogs and cats can also bring the pests inside, so check them and tick-proof your yard. Clear out the leaves and brush where ticks like to hide. Keep your lawn mowed.
More facts about ticks
These arachnids can’t fly or jump but rather wait for a host — whether it be a mammal, bird, reptile or amphibian — to feed on while resting on the tips of grasses and shrubs. They hold on to leaves and grass with their lower legs, a position called “questing.”
As the host passes by, the tick climbs on and finds a place to bite.
Besides Lyme disease, at least 20 known medical conditions can result from tick bites.
CNN’s Elizabeth Landau contributed to this report.
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