Pfizer and Valneva report Phase 3 VALOR trial results showing ~73% efficacy for investigational Lyme disease vaccine PF-07307405 (VLA15), with plans for regulatory submissions.
Written By: Anand Sathappan, BPharm
Reviewed By: Pharmacally Editorial Team
Pfizer and Valneva have reported topline results from the Phase 3 VALOR trial evaluating their investigational Lyme disease vaccine candidate PF-07307405 (also known as LB6V or VLA15). The study demonstrated vaccine efficacy of more than 70% in preventing confirmed Lyme disease cases, marking a major step toward the potential first approved vaccine for the infection.
The multicenter, randomized, placebo-controlled and observer-blinded Phase 3 VALOR trial (NCT05477524) evaluated the vaccine in participants aged five years and older across the United States, Canada, and Europe. Participants were randomized 1:1 to receive four doses of either PF-07307405 or placebo, administered at months 0, 2, and 5–9, followed by a booster one year later before the start of the next Lyme disease season.
In pre-specified analyses, the vaccine demonstrated 73.2% efficacy starting 28 days after the fourth dose during the second Lyme season, with a 95% confidence interval (CI) of 15.8–93.5. A second pre-specified analysis showed 74.8% efficacy from one day after the fourth dose, with a 95% CI of 21.7–93.9, indicating meaningful protection against confirmed Lyme disease cases compared with placebo.
However, the primary endpoint statistical threshold was not formally met because fewer Lyme disease cases than expected occurred during the trial, resulting in the lower bound of the confidence interval falling below the pre-specified threshold in the first analysis. Despite this, Pfizer noted that the clinically meaningful efficacy observed supports continued regulatory progress.
“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,” said Annaliesa Anderson, Ph.D., Senior Vice President and Chief Vaccines Officer at Pfizer. She added that the more than 70% efficacy observed in the VALOR study is highly encouraging and strengthens confidence in the vaccine’s potential to protect against the disease.
Thomas Lingelbach, Chief Executive Officer of Valneva, said the results move the companies closer to delivering a long-awaited preventive option against Lyme disease and highlighted the importance of the collaboration with Pfizer in advancing the program.
PF-07307405 works by inducing the immune system to generate antibodies against the outer surface protein A (OspA) found on Borrelia bacteria present inside the tick. Following vaccination, the body produces antibodies targeting six different OspA serotypes associated with Lyme disease. When an infected tick feeds on a vaccinated individual, these circulating antibodies are taken up by the tick during the blood meal. Inside the tick’s gut, the antibodies bind to the OspA proteins present on the surface of Borrelia bacteria, blocking the bacteria’s ability to migrate out of the tick and into the human host. By interfering with this transmission process, the vaccine helps prevent the bacteria from being passed to humans during a tick bite. The vaccine is designed to protect against the six most common OspA serotypes of Borrelia burgdorferi sensu lato circulating in North America and Europe.
Lyme disease is the most common vector-borne illness in the Northern Hemisphere. The U.S. Centers for Disease Control and Prevention estimate around 476,000 people are diagnosed and treated annually in the United States, while approximately 132,000 cases are reported each year across Europe. Early symptoms often include erythema migrans rash, fatigue, fever, and joint pain, and untreated infections can lead to serious complications affecting the joints, heart, and nervous system.
Pfizer and Valneva plan to submit regulatory filings for the vaccine candidate, supported by the efficacy data and the broader Phase 3 development program. If approved, PF-07307405 could become the first widely available vaccine to prevent Lyme disease.
References
Pfizer and Valneva Announce Lyme Disease Vaccine Candidate Demonstrates Strong Efficacy in Phase 3 VALOR Trial, 23 March 2026, Pfizer and Valneva Announce Lyme Disease Vaccine Candidate Demonstrates Strong Efficacy in Phase 3 VALOR Trial | Pfizer
An Efficacy, Safety, Tolerability, Immunogenicity, and Lot-Consistency Clinical Trial of a 6-Valent OspA-Based Lyme Disease Vaccine (VLA15) (VALOR), ClinicalTrials.gov ID NCT05477524, https://clinicaltrials.gov/study/NCT05477524
About the Writer
Anand Sathappan is a pharmacy graduate with interests in pharmaceutical sciences, pharmacology, and medical writing. He also holds certification in medical coding and has familiarity with pharmacology and healthcare documentation. He has completed the Medical Writing Skills for Beginners program offered by the International Medical Writers Association (IMWA). His work focuses on exploring developments in pharmaceuticals and presenting scientific information in a clear and structured manner.