Lyme disease vaccine shows over 70 percent efficacy in phase 3 trial

Monday 23 March 2026 - 16:20

By: Dakir Madiha

Lyme disease vaccine shows over 70 percent efficacy in phase 3 trial

Pfizer and Valneva said their experimental Lyme disease vaccine achieved more than 70 percent efficacy in a large phase 3 clinical trial, marking a significant step toward the first approved human vaccine for the disease in more than two decades.

Results from the VALOR trial showed the vaccine was 73.2 percent effective in preventing confirmed Lyme disease cases starting 28 days after a fourth dose, and 74.8 percent effective from one day after the fourth dose compared with placebo. The study included 9,437 participants aged five and older across endemic regions in the United States, Canada and Europe.

Despite the strong efficacy results, the trial produced mixed statistical outcomes. The number of Lyme disease cases during the study was lower than expected, and the primary endpoint threshold was not met in the first pre-specified analysis. However, the required statistical benchmark was achieved in a second analysis, and both companies said the results support continued development.

Pfizer said the findings reinforce confidence in the vaccine’s potential to prevent a disease that can cause long-term health complications. Valneva described the results as a step toward addressing a major unmet medical need.

There is currently no approved vaccine for Lyme disease in humans. The only previous vaccine, LYMErix, was withdrawn from the market in 2002 due to declining demand, public concerns and legal challenges, despite a lack of confirmed links to serious side effects.

The need for a vaccine has grown as Lyme disease cases increase. US health authorities estimate that nearly 476,000 people are diagnosed and treated each year, with the disease spreading geographically as tick habitats expand.

The vaccine candidate, known as PF-07307405, works by triggering antibodies against multiple variants of a surface protein of the bacteria Borrelia burgdorferi. When a tick feeds on a vaccinated person, the antibodies are ingested and block transmission of the bacteria.

Pfizer has received fast track designation from US regulators and plans to seek approval in the United States and Europe in 2026. A separate phase 3 trial focused on pediatric safety has also been completed.