Carl Zimmer -- April 24, 2026
The 8-4 vote against reflected concerns that the trial's 18-month follow-up left too many questions about long-term safety, though the FDA is not required to follow its advisers.
An advisory panel to the Food and Drug Administration voted 8 to 4 on Thursday against recommending approval of a Lyme disease vaccine developed by Pfizer and Valneva, citing concerns that available data were insufficient to support a positive benefit-risk determination at this stage.
The majority's objections were not directed at the vaccine's efficacy data, which showed 89 percent protection against confirmed Lyme disease across more than 6,000 participants in phase 3 trials conducted in North America and Europe. The panel's central concern was the 18-month follow-up period, which the majority considered too short to rule out delayed adverse events.
That caution was shaped in part by the history of LYMErix, the only previously licensed Lyme vaccine in the United States, which was withdrawn from the market in 2002 after post-approval reports of arthritis-like symptoms. Later studies found those reports to be unsubstantiated, but the programme did not survive them.
The four dissenting members argued that the majority was applying a standard inconsistent with those used for other approved vaccines. They pointed to the scale of the disease burden — approximately 476,000 Americans are diagnosed with Lyme disease annually, with a significant proportion experiencing long-term symptoms even after treatment — as a factor that weighed in favor of approval with robust post-market surveillance.
Pfizer and Valneva issued a joint statement indicating they would work with the FDA to address the committee's concerns and submit additional data from an ongoing trial extension. The FDA is not bound by advisory committee votes, and a final agency decision on the application remains pending.