It’s that time of year again. The ticks are out in force.

With around 30,000 cases reported each year to the Centers for Disease Control (CDC), Lyme disease has become the most common vector-borne disease in the United States. While that may not sound like a huge number, it’s estimated that the actual figure could be five-fold higher due to underreporting.

It’s transmitted to humans through bites from blacklegged ticks infected with the spiral-shaped bacterium Borrelia burgdorferi. While the disease is rarely fatal, if treatment is absent or delayed it can lead to arthritis, neurologic problems like meningitis or nerve inflammation, and sometimes even heart problems.

Although most patients will fully recover after a course of antibiotics, prevention—as with any disease—is always better than a cure. Such preventive strategies include reducing exposure to the vector, for example by wearing protective clothing, or vaccination. And there was actually a decent, FDA-licensed vaccine available for Lyme disease, but just four years following its approval for use in the human population it was withdrawn by its manufacturers. It's still available for animals.

Why was it withdrawn for human use? In part, due to a shitstorm kicked up by the anti-vaccination movement.

Developed in the ‘90s by pharmaceutical company SmithKline Beecham (now GlaxoSmithKline), LYMErix was the only licensed Lyme disease vaccine on the market. The vaccine was based on one of the surface proteins expressed by the disease-causing bacterium, which was used to evoke an immune response in the individual. Clinical trials involving more than 10,000 individuals found that LYMErix reduced new infections in adults by close to 80% and conferred protection to 100% of children. Additionally, no serious side-effects were observed.

Despite these positive results, the vaccine was withdrawn from the U.S. market in 2002 due to a combination of factors. Although it was considered a cost-effective approach for Lyme disease, its high cost resulted in slow uptake in clinical settings and reluctance of insurance companies to cough up for it. This, combined with the emergence of a hypothesis that the vaccine sparked immune responses that resulted in arthritis, caused the vaccine’s popularity to plummet.

The idea that the vaccine could cause this “autoimmune arthritis” stemmed from a hypothesis, named the molecular mimicry hypothesis, which suggested that the protein used in the vaccine displayed similarity to a protein found in the human body, but was still different enough to be recognized as foreign by the immune system. This would mean that, alongside attacking the foreign bacterial protein, the immune system would also start targeting the normal human protein and thus lead to an autoimmune reaction.

Within just one year of the vaccine reaching the market, reports of adverse effects began popping up left, right and center, conveniently mostly about musculoskeletal pain or swelling as would be expected in patients suffering from arthritis. The media then soon cottoned on and began running sob stories on personal experiences that were guaranteed to draw in readers, fuel fear and spark public outcry.

This was enough to spur investigations and safety surveillance, both of which failed to find any evidence for either the molecular mimicry hypothesis nor any spikes in arthritis diagnoses. Yet with an increasing number of lawsuits filed against the manufacturers and its decreasing support among the public, encouraged by anti-vaccination groups, the vaccine was pulled from shelves.

It’s disappointing to see that an effective vaccine was withdrawn due to lawsuits and poor sales fueled by pressure from anti-vaccination groups and fear-mongering from the media, all the while the burden of Lyme disease has continued and even worsened. This highlights the need for better public education around important topics such as this, which seems to be an ongoing issue that is not going to be easy to tackle when battling against the blessing and curse that is the internet.