Valneva and Pfizer's experimental Lyme disease vaccine VLA15 has shown encouraging results in a phase 2 study, demonstrating that second booster injections generate immune responses equivalent to first booster doses. The findings from the VLA15-221 study support the vaccine's intended use as an annual shot administered before Lyme disease season.
Strong Booster Response Across Age Groups
The phase 2 data revealed that a second booster injection stimulated a robust immune response that matched the strength seen after the first booster dose. "We are encouraged by [this] data, which support[s] the potential benefit of booster doses across all examined age groups," commented Juan Carlos Jaramillo, Valneva's chief medical officer. "Each new set of positive data brings us one step closer to potentially bringing this vaccine to both adults and children living in areas where Lyme disease is endemic."
VLA15 targets the outer surface protein A (OspA) of the Borrelia burgdorfii bacteria that causes Lyme disease. Previous phase 2 results using a two- or three-dose regimen demonstrated immunogenicity with no vaccine-related serious adverse events.
Addressing Growing Disease Burden
Lyme disease represents the most common vector-borne illness in the Northern Hemisphere, characterized by a distinctive rash that can be accompanied by flu-like symptoms. In severe cases, patients experience debilitating tiredness and aches that persist for years. While antibiotics can effectively treat Lyme disease, a preventive vaccine is needed for individuals who spend significant time outdoors.
The disease burden has increased substantially, with annual reported cases tripling since the 1990s according to Centers for Disease Control and Prevention data. The CDC estimates that approximately 476,000 people in the US are diagnosed and treated for Lyme disease annually, while 129,000 cases are reported each year in Europe. The reasons for this increase aren't well understood but could relate to increased deer populations, reforestation efforts, climate change, and population shifts from urban to suburban areas.
Phase 3 Trial Challenges and Timeline Adjustments
Valneva and Pfizer's phase 3 program, which began in 2022, encountered significant setbacks when some clinical trial sites failed to adhere to Good Clinical Practice standards. This compliance issue led to the discontinuation of approximately 50% of US patients in the VALOR study.
As a result of these challenges, the companies now predict filing for VLA15 approval in the US and Europe in 2026, representing a delay from their earlier 2025 target. The first data from the phase 3 trial is expected by the end of 2025, marking a critical milestone for this first-in-class vaccine candidate.
Historical Context and Competition
The Lyme disease vaccine landscape has been challenging historically. GSK (then SmithKline Beecham) developed Lymerix in the 1990s but withdrew it from the market in 2002 after settling a class action lawsuit claiming injuries from side effects, amid broader anti-vaccine sentiment.
Currently, Moderna is developing mRNA-based vaccines for Lyme disease and recently began recruiting patients for a phase 1/2 trial, representing emerging competition in this space.
Strategic Partnership Evolution
In 2022, Pfizer restructured its alliance with Valneva, taking an 8% stake in the French vaccine developer for approximately $95 million while reducing its share of VLA15 development costs. Pfizer had initially paid $130 million upfront to license rights to VLA15 in 2020, demonstrating sustained commitment to the program despite the development challenges.
