Investigational Lyme Disease Vaccine Shows More Than 70% Efficacy in Phase 3 VALOR Trial

An investigational Lyme disease vaccine candidate demonstrated more than 70% efficacy in preventing confirmed cases of Lyme disease in a phase 3 clinical trial, according to topline results announced by Pfizer and Valneva.

The vaccine candidate, PF-07307405 (LB6V), is a multivalent protein subunit vaccine targeting outer surface protein A (OspA) of Borrelia burgdorferi and is currently the most advanced Lyme disease vaccine in clinical development.

“Lyme disease can cause potentially serious consequences – where individuals and families face symptoms that can disrupt daily life, work, and long-term health – and there is currently no vaccine available,” Annaliesa Anderson, PhD, Senior Vice President and Chief Vaccines Officer, Pfizer, said in a press release. “The efficacy shown in the VALOR study of more than 70% is highly encouraging and creates confidence in the vaccine’s potential to protect against this disease that can be debilitating.”

In the phase 3 VALOR trial (NCT05477524), the vaccine demonstrated:

• 73.2% efficacy from 28 days after the fourth dose (season 2) in reducing confirmed Lyme disease cases vs placebo (95% CI, 15.8–93.5)
• 74.8% efficacy from 1 day after the fourth dose (season 2) (95% CI, 21.7–93.9)

Although fewer cases than expected were accrued during the study period and the predefined primary endpoint criterion was not met in the first analysis, the lower bound of the confidence interval exceeded 20 in the second analysis, which investigators described as clinically meaningful.

The vaccine was reported to be well tolerated, with no safety concerns identified at the time of analysis.

The VALOR study was a multicenter, randomized, placebo-controlled, observer-blinded trial conducted in regions with high Lyme disease incidence across the United States, Canada, and Europe.

Participants aged 5 years and older were randomized 1:1 to receive either the vaccine or saline placebo in a 4-dose series administered at months 0, 2, and 5–9, followed by a booster dose approximately one year later before the subsequent Lyme season.

PF-07307405 targets six OspA serotypes of Borrelia burgdorferi sensu lato, covering the most prevalent strains in North America and Europe.

The vaccine induces antibodies that are ingested by ticks during feeding, preventing the bacteria from leaving the tick and being transmitted to humans.

Based on the phase 3 findings, Pfizer indicated it plans to proceed with submissions to regulatory authorities.

“The efficacy shown in the VALOR study of more than 70% is highly encouraging and creates confidence in the vaccine’s potential to protect against this disease that can be debilitating,” Anderson added in the press release.

References:

1. An Efficacy, Safety, Tolerability, Immunogenicity, and Lot-Consistency Clinical Trial of a 6-Valent OspA-Based Lyme Disease Vaccine (VLA15) (VALOR). ClinicalTrials.gov identifier: NCT05477524. Updated September 29, 2025. Accessed April 8, 2026. https://clinicaltrials.gov/study/NCT05477524
2. Pfizer. Pfizer and Valneva Announce Lyme Disease Vaccine Candidate Demonstrates Strong Efficacy in Phase 3 VALOR Trial. News release. March 23, 2026. Accessed April 8, 2026. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-valneva-announce-lyme-disease-vaccine-candidate