Thanks to vaccines, the number of COVID-19 cases has plummeted in the U.S. and restrictions are being lifted across the country. But as we return to our normal activities, we face a more familiar summertime scourge. We’re in the thick of Lyme disease season, the two-month run from early June to the end of July when 85 percent of infections take place. Surprisingly, vaccines may have allowed us to avoid this epidemic, too. As I learned during my own recent bout with Lyme disease, a vaccine has existed for decades, but it’s no longer available.
It’s yet another frustrating aspect of this mysterious disease. One bite from a tiny, hard-to-detect tick can lead to a host of odd symptoms, including arthritis, serious cardiac issues, and neurological damage in the most severe cases. The disease is easy to treat once you get a diagnosis, but that can be elusive. And while work is underway to develop a new and better vaccine, it may take years to come to market. Here’s what we know about how the disease works, and what you can do to stay safe.
Lyme disease is dangerous for us — and a tragedy for the bacteria
Lyme disease is caused by a bite from a deer tick, also known as black-legged ticks or Ixodes scapularis. The tick attaches by jamming a barb-lined spear into your skin, gluing itself in place with a sticky substance, and injecting a fluid into the wound that prevents the blood from clotting. That’s gross, but it’s not health-endangering.
The problem is when the parasite has itself been parasitized by a spiral-shaped bacteria called Borrelia burgdorferi or one of its closely related cousins. As the tick slurps up your blood, bacteria make their way from its gut to its salivary glands and then into your body.
For the Borrelia, this is a terrible tragedy. The bacteria was hoping to find itself was inside the body of one of its natural hosts: a mouse, bird, or deer. It has evolved to live inside these animals as a harmless passenger. “Through evolution, parasites come to an agreement with their hosts that they won’t harm each other,” says Sam Telford, a professor of epidemiology at the Tufts Cummings School of Veterinary Medicine who’s a leading expert on Lyme disease.
When a host animal is bitten by another tick, the bacteria will move on, and the endless dance will continue. But humans are a dead end: It’s unlikely that any human suffering the deeply uncomfortable effects of Borrelia infection will be wandering around in a woodsy habitat where it might get re-parasitized by another tick. So as nasty as Lyme disease is for us, for the Borrelia, it’s the end of the road.
You probably won’t see the tick that infects you
After hatching out of an egg, the deer tick passes through three stages: larva, nymph, and adult. At each stage, the tick must find a new host and feed. Since when they hatch they are uninfected by Borrelia, larva can’t cause Lyme disease. And adult ticks are easy to feel and spot when they crawl on you, so they’re also unlikely to latch on and pass along the disease. The really dangerous vectors are the nymphs, about 15 percent of which carry Borrelia and which are so tiny — less than a tenth of an inch long, about the size of a poppy seed — that it’s very difficult to see them. Most people who come down with Lyme disease don’t notice that they’ve been bitten.
Tick nymphs are active in the spring, lurking in tall grass or shrubbery, waiting for a host to drop down onto. Since this time of year is also when human beings are most likely to be frolicking amid the greenery with lots of tasty exposed flesh, Lyme disease cases spike around now.
No one knows why Lyme disease makes you sick
Compared to malaria, which is caused by single-cell organisms that can be seen teeming in each drop of blood under the microscope, Borrelia infects the human body in relatively low concentrations. In about three-quarters of all cases it causes a circular, itchy rash called Erythema migrans around the site of the original tick bite. Beyond that, it’s not clear exactly why the bacteria makes us sick. In many people, the infection doesn’t cause any symptoms. For the unlucky, the disease hits hard, with a suite of symptoms that includes fever, muscle aches, joint pain, nausea, and a general sense of feeling absolutely miserable. If left untreated, Lyme can lead to arthritis, neurological disorders like partial facial paralysis, or cardiac disease.
For me, the worst part was shooting headaches so intense they’d wake me up in the middle of the night. The constant pain made me so uncomfortable that my personality was changing: I became impatient, sullen, short-tempered. When my doctor’s office called to say that my test results had come back positive, I was elated: I knew that within a day or two of starting a course of antibiotics, I’d gotten a reprieve from a misery that otherwise could have dragged on until God knows when.
The more our suburbs sprawl, the worse Lyme gets
The first case of Lyme wasn’t discovered until 1975, when two mothers in Lyme, Connecticut, pressed for scientists to explain why children in their neighborhood were coming down with a form of arthritis.
A half-century later, Lyme disease is all over the place. The Centers for Disease Control estimates that as many as half a million Americans come down with it each year, and cases are reported in all 50 states, as well as in Europe and Asia. But it isn’t spreading, in the way that a disease like COVID spreads, by being passed from person to person. Instead, the bacillus has been there all along, weaving its way between tick and warm-blooded hosts. What’s different is that we’ve inserted ourselves into this ancient dance. “We’ve created the conditions over the last 40 or 50 years,” says Telford, by increasingly building housing in areas that were once forest or farm fields, allowing foliage to grow up of the kind that deer like to eat, and by stopping hunting that would otherwise keep deer populations in check. “There have always been little patches of vegetation that no one ever stumbled across,” Telford says. “With suburbanization these have grown up and spread.”
A safe and effective vaccine exists, but you can’t get it
After Borrelia burgdorferi was identified in 1983 as the cause of Lyme disease, researchers went to work developing a vaccine, and in short order they found success. SmithKlineBeecham tested its three-dose LYMErix vaccine on some 10,000 volunteers and found that it was 76 percent effective, with no significant side effects. In 1998 the FDA approved it, and areas where the vaccine was widely administered showed sharp drops in Lyme disease.
In a perfect world we’d still be using LYMErix today, and hundreds of thousands of people might have been spared the disease, including me. But it was not to be. Within a year of the vaccine’s introduction, anecdotal reports began circulating about possible side effects. The media reported on the plight of “vaccine victims,” and a Philadelphia law firm filed a class-action lawsuit against SmithKlineBeecham. The furor prompted the FDA to review the safety data; it concluded that the concerns were unwarranted. But the damage had been done. Demand for the vaccine fell off so precipitously that the manufacturer simply pulled it from the market.
That’s not the end of the story, though. Pfizer has teamed up with the French pharmaceutical company Valneva to develop a new Lyme disease vaccine called VLA15 that will target a broader range of Borrelia subspecies, meaning that it will, hopefully, have a significantly higher overall efficacy. Currently undergoing phase 2 trials, the vaccine is unlikely to see approval before 2025.
Meanwhile, earlier this year a company called MassBiologics began phase 1 trials of a shot called Lyme PrEP that contains monoclonal antibodies against Borrelia. Unlike a vaccine, this doesn’t prod your immune system to take up arms against the invader, but instead delivers the antibodies that can kill the bacteria all by themselves. While the approach has been proven 100 percent effective in animal tests, according to the researchers, the work isn’t as far along as the VLA15 vaccine, so it’s probably further from approval.
If you have Lyme disease, you may have another illness, too
Ticks have been called the dirty syringes of the animal kingdom, swapping infected blood indiscriminately among their hosts. So if Lyme disease were the only thing we could get from these vermin, we’d be lucky. But we’re not. There are a half-dozen or more other tick-born pathogens that can get passed on along with Borrelia, including Babesia microti and Anaplasma phagocytophila (both of which can cause fever and death). “When someone is diagnosed with Lyme disease they should at least be tested for other pathogens,” Telford says.
While waiting for new treatments to come along, your best bet is to take some simple precautions to avoid encountering Borrelia in the first place: Wear long-sleeved clothes when in tick habitat, apply DEET insect repellent, and check yourself for embedded ticks. If worse comes to worst and you come down with symptoms, talk to your doctor about getting tested. Antibiotics like doxycycline are highly effective against the disease even in its more serious later stages.
After all, says Telford, Lyme disease is a drag, but you shouldn’t let the fear of it ruin your life: “People should enjoy the outdoors,” he says.