Pfizer and Valneva said Monday their Lyme disease vaccine showed more than 70% efficacy in a late-stage study, even as it missed its main goal.
U.S.-listed shares of the French drugmaker tumbled more than 35% in premarket trading following the update, while Pfizer was flat.
The vaccine demonstrated 73.2% efficacy starting 28 days after the fourth dose in reducing confirmed Lyme disease cases, compared to the placebo.
However, fewer-than-anticipated Lyme cases during the study led to the trial falling short of the key requirement that the vaccine should still be at least 20% effective even in the worst-case scenario. In the first analysis, it came in lower, at 15.8%.