Promising results from a Lyme disease vaccine study conducted in Finland

Vaccination against tick-borne Lyme disease may become possible within the next few years

Ticks have become well established in Finland and are now found throughout the country, with the exception of the northernmost parts of Lapland. They are most common in coastal areas and the archipelago. Tick populations have increased substantially in Finland and elsewhere in Europe. Warmer summers and favourable conditions, including the availability of host animals, have contributed to the increase in tick populations, while the incidence of tick-borne diseases has also risen. 

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Lyme disease is the most common tick-borne disease in Finland

Ticks transmit two diseases: tick-borne encephalitis (TBE) and Lyme disease.

Lyme disease is by far the most common tick-borne infection in Finland, occurring many times more frequently than tick-borne encephalitis (TBE). Each year, approximately 60–90 people are diagnosed with TBE in Finland, while around 7,000 people are diagnosed with Lyme disease. Unlike TBE, Lyme disease occurs throughout almost the entire country. On average, the bacterium that causes Lyme disease is present in 20–25% of ticks, although the prevalence varies considerably by region. 

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A vaccine against tick-borne encephalitis (TBE) is already available. However, there is currently no approved vaccine against Lyme disease for human use. 

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Promising results from the Lyme disease vaccine study

Between 2022 and 2025, an international study (C4601003) was conducted in Finland to evaluate the efficacy and safety of VLA15, a Lyme disease vaccine developed by Pfizer. Approximately 300 Finnish children over five years of age and adults participated in the study through FVR’s research clinics. Vaccinations administered as part of the study have been recorded in Finland’s Kanta Services (MyKanta). 

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According to the preliminary results, the vaccine provided good protection against Lyme disease. Following the booster dose, vaccine efficacy was 73%. The vaccine was well tolerated, and no safety concerns were identified. 

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The study results will next undergo peer review. If the findings continue to be positive, vaccine development will proceed as planned, and following regulatory review, the vaccine could potentially become available in 2027.