Pfizer and Valneva's PF-07307405 shows ~74% efficacy against Lyme disease in Phase III VALOR trial

Pfizer (NYSE: PFE) and Valneva (Nasdaq: VALN) [reported](https://www.businesswire.com/news/home/20260322114817/en/Pfizer-and-Valneva-Announce-Lyme-Disease-Vaccine-Candidate-Demonstrates-Strong-Efficacy-in-Phase-3-VALOR-Trial) Phase III results for their Lyme disease vaccine candidate PF-07307405 (LB6V, formerly VLA15), showing approximately 73–75% efficacy in preventing confirmed Lyme disease in individuals aged five and older — a result that, if accepted by regulators, would yield the first approved human vaccine against the tick-borne illness. The [VALOR trial](https://clinicaltrials.gov/study/NCT05477524) (NCT05477524) is a multicenter, placebo-controlled, randomized, observer-blinded Phase III study conducted across sites in the U.S., Canada, and Europe in areas with high Lyme disease incidence. Participants aged five years and older were randomized 1:1 to receive four doses of PF-07307405 or saline placebo, administered at months 0, 2, and 5–9, with a fourth dose given approximately one year later ahead of the second Lyme disease season. In two pre-specified analyses, the vaccine demonstrated efficacy of 73.2% (95% CI: 15.8, 93.5) from 28 days post-dose four and 74.8% (95% CI: 21.7, 93.9) from one day post-dose four, each measuring the reduction in confirmed Lyme disease cases relative to placebo. However, the trial accrued fewer Lyme disease cases than anticipated over the study period. As a result, the primary endpoint — the first pre-specified analysis — did not meet its pre-determined statistical success criterion, which required the lower bound of the 95% confidence interval to exceed 20. The second pre-specified analysis did clear that threshold. Pfizer stated it remains confident in the vaccine's potential and is planning regulatory submissions. The vaccine was well tolerated, with no safety concerns identified at the time of analysis, according to the companies. PF-07307405 is a multivalent protein subunit vaccine targeting outer surface protein A (OspA) of Borrelia burgdorferi sensu lato, the group of bacteria responsible for Lyme disease. The vaccine covers six OspA serotypes prevalent in North America and Europe. Its mechanism is distinct: antibodies generated in a vaccinated individual are ingested by a feeding tick, and these antibodies bind OspA on Borrelia inside the tick, preventing the bacterium from migrating out of the tick and into the human host. The approach effectively neutralizes the pathogen before it reaches the person's body. The statistical nuance in these results warrants attention. While the point estimates of efficacy — above 70% in both analyses — are within the range regulators have historically accepted for vaccine approvals, the wide confidence intervals and the failure to meet the pre-specified statistical criterion on the primary analysis introduce uncertainty. The lower bound of 15.8% in the first analysis is well below the 20% threshold the trial was designed to clear. Pfizer's decision to proceed with regulatory filings rests partly on the second analysis meeting its threshold and the overall clinical meaningfulness of the effect size. How the US FDA and European regulators weigh this distinction will be closely watched. No human vaccine for Lyme disease is currently approved. A previous OspA-based vaccine, LYMErix, developed by SmithKline Beecham (now GSK), received FDA approval in 1998 but was withdrawn from the market in 2002 amid declining sales and safety concerns that were never substantiated in post-marketing studies. The absence of a successor for more than two decades has left prevention reliant on tick avoidance measures and prompt tick removal. The Centers for Disease Control and Prevention estimates approximately 476,000 people in the U.S. are diagnosed and treated for Lyme disease annually, and roughly 132,000 cases are reported each year in European countries with surveillance systems. The geographic range of Ixodes ticks continues to expand, driven in part by climate change. Pfizer holds exclusive rights to manufacture and commercialize PF-07307405 under a collaboration and license agreement with Valneva established in April 2020. Valneva, a specialty vaccine company based in Lyon, France, initiated the program's earlier development. Two prior [Phase II studies](https://clinicaltrials.gov/study/NCT04239395) have been completed. The companies described the VALOR trial as one of two pivotal Phase III studies for the candidate, though details on the second pivotal study were not provided in the announcement. Pfizer stated it is planning submissions to regulatory authorities based on these data, though specific timelines and the agencies targeted were not disclosed. Whether the statistical profile of the VALOR results will require additional data or supportive analyses to satisfy regulators remains an open question — one that will shape the path toward what would be a first-in-class product in a field that has waited more than two decades for a vaccine option. --- Spot something wrong? [Report an issue with this article](https://newsgen-prod.reframedata.com/feedback/lyme-disease-vaccine-pfizer-and-valnevas)