Pfizer said on Mar. 23 that it remains confident in its investigational Lyme disease vaccine, developed with Valneva, despite the candidate missing its primary endpoint in a late-stage clinical trial.
The announcement is significant because there is currently no approved vaccine for Lyme disease, a tick-borne infection that affects thousands each year. The companies reported that their vaccine candidate, PF-07307405 (LB6V), showed an efficacy of 74.8% from one day after the fourth dose compared to placebo and slightly lower at 73.2% at the same timepoint. However, the Phase 3 VALOR trial did not meet its predetermined primary endpoint of achieving a specific confidence interval.
Pfizer attributed this outcome to fewer than expected cases of Lyme disease occurring during the study period. “Given the clinically meaningful efficacy and the fact that the 95% confidence interval lower bound was above 20 in the second pre-specified analysis, Pfizer is confident in the vaccine’s potential and is planning submissions to regulatory authorities,” Pfizer said Monday.
RBC Capital Markets analysts noted that when LB6V's application reaches U.S. regulators, "it could be met with a sympathetic ear," referencing recent statements by Health and Human Services Secretary Robert F. Kennedy Jr., who has called for greater efforts to address Lyme disease and convened a panel on prevention and care in December 2025.
Analysts also pointed out challenges ahead for Pfizer and Valneva if approved, citing GSK’s LYMERix—a previous Lyme vaccine withdrawn from market due to low demand despite similar efficacy rates—as an example from history.
Despite these hurdles, RBC continues to forecast peak unadjusted sales of $525 million for LB6V based on current unmet needs and renewed regulatory attention. The partnership between Pfizer and Valneva began in April 2020 with Valneva eligible for up to $308 million under their agreement.
