Lyme disease vaccine candidate PF-07307405 has demonstrated significant efficacy in protecting both adults and children from the most common vector-borne illness in the Northern Hemisphere. Pfizer Inc. and Valneva SE announced today that their investigational multivalent vaccine successfully met key clinical benchmarks in the Phase 3 VALOR (Vaccine Against Lyme for Outdoor Recreationists) trial. With efficacy rates exceeding 70%, this development marks a historic turning point in the fight against a disease that has lacked a preventative human vaccine for over two decades.
A Breakthrough for the Lyme Disease Vaccine Candidate
The partnership between Pfizer and Valneva, established in 2020, was formed to address the growing public health crisis posed by Borrelia burgdorferi, the bacterium transmitted through the bite of infected black-legged ticks. As global temperatures rise and tick habitats expand, the need for a Lyme disease vaccine candidate has never been more urgent.
According to the Centers for Disease Control and Prevention (CDC), approximately 476,000 Americans are diagnosed and treated for Lyme disease annually. In Europe, the burden is similarly high, with over 130,000 cases reported each year. The “VALOR” trial was designed to test whether the vaccine could provide a robust shield for those living in or visiting high-risk endemic areas.
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Clinical Success: The VALOR Study Results
The Phase 3 trial was a multicenter, randomized, and observer-blinded study involving over 6,000 participants aged five years and older. The data revealed that the Lyme disease vaccine candidate was highly effective:
- 73.2% Efficacy: Measured 28 days after the fourth dose (booster) during the second Lyme season.
- 74.8% Efficacy: Observed as early as one day post-dose 4.
Phase 3 VALOR Trial Efficacy Summary
| Analysis Point | Vaccine Efficacy (VE) | 95% Confidence Interval (CI) | Clinical Context |
| 28 Days Post-Dose 4 | 73.2% | 15.8% – 93.5% | Primary analysis window for Season 2 |
| 1 Day Post-Dose 4 | 74.8% | 21.7% – 93.9% | Immediate protection after booster |
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How the Lyme Disease Vaccine Candidate Protects Patients
Unlike many vaccines that prime the human immune system to fight a pathogen after it enters the body, this Lyme disease vaccine candidate utilizes a unique mechanism of action. It targets the Outer Surface Protein A (OspA) of the Borrelia bacteria.
When a tick bites a vaccinated individual, it ingests the antibodies present in the person’s blood. These antibodies then neutralize the bacteria within the tick’s midgut before they can ever be transmitted to the human host. Because the vaccine is 6-valent, it covers the six most common OspA serotypes prevalent in both North America and Europe, providing broad regional protection.
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Safety and Tolerability in Children and Adults
One of the most significant hurdles for any new pharmaceutical product is the safety profile. Fortunately, the Lyme disease vaccine candidate was well-tolerated across all age groups in the VALOR study. No safety concerns were identified by the independent Data Safety Monitoring Committee.





