Rise in Lyme Disease Cases and Vaccine Development
Cases of Lyme disease have increased by more than 20% in England over the past year, according to public health experts, as pharmaceutical companies develop new vaccines and treatments to combat this tick-borne illness.
Data from the UK Health Security Agency (UKHSA), released as part of its annual report, shows there were 1,168 laboratory-confirmed cases of Lyme disease in 2025, compared to 959 cases in 2024, marking a 22% rise. However, this number is comparable to the 1,151 confirmed cases reported in 2023.
Additionally, two probable cases of tick-borne encephalitis complex were identified in 2025, bringing the total locally acquired cases to six since the virus was first detected in the UK in 2019.
Dr Claire Gordon, head of the rare and imported pathogens laboratory at UKHSA, stated: "While the number of laboratory-confirmed acute cases of Lyme disease in 2025 is an increase on numbers reported in 2024, we expect overall case rates to vary year to year depending on awareness, testing rates and factors that impact outdoor activities such as weather. Broader trends in 2025 remain consistent."
About Lyme Disease and Tick Distribution
Lyme disease is caused by the bacterium Borrelia burgdorferi, which resides in the gut of ticks—small arachnids found in grassy and wooded areas that feed on the blood of birds and mammals, including humans.
"In recent years, we have seen an increasing geographical distribution of ticks across the UK," Gordon explained. "But tick numbers continue to vary due to changes in weather conditions, climate trends, habitat changes and shifting host populations."
Symptoms of Lyme disease include a characteristic bullseye rash, fever, muscle and joint pain, and lethargy. If untreated, the disease can become chronic, and some patients report persistent symptoms even after antibiotic treatment.
Not all ticks carry the Lyme bacteria, and rapid removal of ticks is believed to reduce the risk of infection. While various medications and vaccines are available to protect pets from Lyme disease, human prevention focuses on measures such as using repellents, covering exposed skin outdoors, and wearing light-colored clothing to spot and remove ticks promptly.
Challenges in Human Vaccine Development
Linden Hu, professor of immunology at Tufts Medical School, noted differences between veterinary and human approaches to Lyme disease prevention. Pet owners are generally more willing to medicate their animals than themselves or family members, and clinical trials in humans are more difficult to conduct.
"It’s easier to do studies in animals because you can control the situation. You can put infected ticks on them to test if it’s going to work, which you really can’t do with humans," Hu said. He added that real-world or "field trials" are costly and risky due to uncertainty about the number of Lyme cases that will occur.
A human Lyme vaccine, LYMErix, was previously available in the US, with trials indicating an efficacy of approximately 76%. However, it was withdrawn from the market after poor uptake.
Hu explained, "There were a couple of things that coalesced to cause the low sales," including the US Centers for Disease Control and Prevention recommending the vaccine only for people at high risk. There were also concerns that the vaccine might be linked to arthritis, and although unproven, the negative media coverage surrounding the vaccine contributed to low demand."
New Vaccines and Treatments in Development
Several new treatments are under development, including a vaccine Hu has worked on that is currently in phase 2 clinical trials, as well as another vaccine developed by Pfizer and Valneva.
Hu emphasized that both vaccines aim to avoid triggering the immune pathway suspected of causing arthritis in some LYMErix recipients.
However, development has faced challenges. The Pfizer/Valneva vaccine showed an efficacy of over 70%, but the results were not as statistically robust as hoped. Despite this, the vaccine is planned to be submitted for regulatory approval.
Other approaches include a vaccine from Tonix Pharmaceuticals intended for administration before tick exposure, and a drug called lotilaner, developed with Tarsus Pharmaceuticals, which is already used to protect dogs and cats. Unlike vaccines, lotilaner kills ticks directly rather than targeting the bacteria.
Hu stated, "Lotilaner works rapidly by killing the ticks before they have a chance to transmit Lyme or, potentially, other diseases."
Public Perception and Future Outlook
Julia Knight from the charity Lyme Disease UK noted uncertainty about whether a Lyme vaccine would be adopted in the UK, given the relatively low official figures, which are likely underestimates. This is partly because approximately 70% of people with Lyme disease develop the characteristic rash and are treated immediately without laboratory confirmation, and because Lyme disease can be missed or misdiagnosed.
"Obviously any advances in science that prevents Lyme disease is always welcome, but whether people will welcome a vaccine or not in the current climate of vaccine hesitancy remains to be seen," Knight said.
