Pfizer-Valneva Lyme Vaccine Shows 73% Efficacy in Phase 3

Pfizer and French biotech company Valneva announced on Monday that their experimental Lyme disease vaccine demonstrated more than 70 percent efficacy in preventing infections during a late-stage clinical trial, though it fell short of its primary statistical goal due to fewer cases than anticipated.

The vaccine, known as PF-07307405, was tested in the Phase 3 VALOR study involving about 9,400 participants aged 5 and older from Lyme-endemic regions in the United States, Europe and Canada. Participants received either the vaccine or a saline placebo. The trial began with around 18,000 enrollees, but roughly half were removed in 2023 after quality issues surfaced at a third-party clinical site.

In the first prespecified analysis, the vaccine showed 73.2 percent efficacy in reducing confirmed Lyme disease cases starting 28 days after the fourth dose, compared to placebo. However, this missed the primary endpoint because the lower bound of the 95 percent confidence interval was 15.8 percent, below the required threshold of 20 percent. The companies attributed the shortfall to a lower-than-expected number of infections, which limited the data points available for analysis.