Pfizer and Valneva have reported that their phase 3 trial evaluating a Lyme disease vaccine candidate did not meet its primary endpoint, citing a lower-than-expected number of Lyme disease cases during the study period. Despite this outcome, both companies have stated they intend to proceed with regulatory submissions.
The late-stage Valor trial enrolled 9,437 participants aged five years and older across regions in the United States, Canada, and Europe, where Lyme disease incidence is considered high. The investigational vaccine, known as PF-07307405 or VLA15, was administered in a four-dose schedule. Participants received an initial dose followed by a second dose at two months, a third dose between five and nine months, and a fourth dose shortly before the next Lyme disease season.
The primary objective of the study was to evaluate the vaccine’s efficacy in reducing confirmed Lyme disease cases 28 days after the fourth dose. The results showed an efficacy rate of 73.2%. However, the lower bound of the 95% confidence interval was calculated at 15.8%, falling short of the predefined 20% threshold required to meet the primary endpoint.
According to the companies, the shortfall was attributed to an insufficient number of Lyme disease cases recorded during the trial. They stated that “fewer than anticipated Lyme disease cases were accrued over the study period,” which impacted the statistical outcome of the analysis.
This is not the first challenge encountered during the trial. In 2023, Pfizer and Valneva removed approximately half of the originally enrolled participants after identifying good clinical practice violations at certain U.S. trial sites managed by a third-party operator. At that time, both companies indicated that the issue would delay their regulatory submission timeline by approximately one year.
In the latest update, the companies highlighted results from a secondary pre-specified analysis. In this assessment, vaccine efficacy reached 74.8% one day after the fourth dose, with the lower bound of the confidence interval exceeding the 20% threshold. Based on this finding, Pfizer stated it remains confident in the vaccine’s potential and plans to submit data to regulatory authorities.
Pfizer’s Chief Vaccine Officer, Annaliesa Anderson, Ph.D., said the observed efficacy above 70% is encouraging and supports confidence in the vaccine’s ability to provide protection against Lyme disease. Her comments were presented as part of the company’s official statement.
Lyme disease is a vector-borne illness primarily found in the Northern Hemisphere. The companies estimated that approximately 476,000 cases occur annually in the United States, with around 129,000 cases reported each year in Europe. They also noted that the geographic spread of the disease has increased over time.
Currently, no Lyme disease vaccines are approved for use in the United States. A previous vaccine developed by GSK was withdrawn from the market in 2002 due to low demand.
For Valneva, the vaccine program represents a significant component of its pipeline. Chief Executive Officer Thomas Lingelbach previously described the VLA15 program to analysts as a key driver for the company’s future development and strategic direction.
The collaboration between Pfizer and Valneva dates back to a 2020 agreement. Under the terms, Valneva received an upfront payment of $130 million and remains eligible for additional milestone payments tied to development and early commercialization, as well as tiered royalties starting at 19% on future sales. Valneva is responsible for 30% of development costs, while Pfizer retains sole commercialization rights.
Valneva and Pfizer Report Phase 3 Lyme Vaccine Results
Valneva and Pfizer have announced Phase 3 trial results for their Lyme disease vaccine candidate, delivering a setback while still maintaining forward momentum. The update shows that Valneva and its partner did not fully meet all primary expectations in the late-stage study, yet Valneva remains confident in the overall data package and its potential for regulatory submission.
Mixed Outcomes but Continued Confidence
Despite the Phase 3 miss, Valneva emphasized that the vaccine demonstrated meaningful immune responses and a favorable safety profile. According to Valneva, the data still supports the potential benefit of the vaccine in preventing Lyme disease, a condition with growing incidence in several regions. Valneva highlighted that no major safety concerns were identified, reinforcing confidence in the candidate’s long-term viability.
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