Pfizer and Valneva presented the detailed Phase 3 results for LB6V, their six-valent OspA-based Lyme disease vaccine candidate, at IDWeek 2026, and the detail explains why the March topline readout was described as mixed. The vaccine, studied in about 9,400 participants aged 5 and older in Lyme-endemic regions of North America and Europe, showed efficacy of roughly 73 to 75 percent against confirmed Lyme disease. The trial’s primary analysis, however, required the lower bound of the 95 percent confidence interval for efficacy to exceed 20 percent, and it came in at 15.8 percent. A second prespecified analysis met the threshold, with a lower bound of 21.7 percent. Fewer Lyme cases occurred during the study than the trial was powered for, which widened the confidence intervals. Safety profiles were similar across groups, Endpoints News reported.
The regulatory position is already live. The European Medicines Agency started its review of the marketing authorisation application in August 2026, and the IDWeek presentation title itself states the findings support the potential to provide clinically meaningful antibody-associated protection. Pfizer’s case to regulators rests on the point estimate, the second analysis, and the antibody correlate; the sceptical case rests on the missed prespecified criterion in the primary analysis, which exists precisely to stop sponsors from choosing the friendlier analysis after the fact.
The commercial history hangs over the file. The only previously licensed Lyme vaccine, LYMErix, was withdrawn in 2002 after demand collapsed, and no vaccine has been available since, in a disease with hundreds of thousands of estimated annual cases in the United States and Europe combined. A licensed LB6V would reopen that market with a broader six-serotype construct. Whether it gets the chance now depends on how the EMA, and then the FDA, weigh a near miss.