For the first time since LYMErix was pulled from the U.S. market in 2002, a Lyme disease vaccine is on the verge of regulatory approval — and the Phase 3 trial results suggest it is substantially effective in both adults and children as young as 5 years old. Pfizer and Valneva announced on March 23, 2026 that their investigational 6-valent OspA-based Lyme disease vaccine candidate, PF-07307405 (LB6V, formerly known as VLA15), demonstrated efficacy of 73.2 to 74.8 percent in preventing confirmed Lyme disease cases in the Phase 3 VALOR (Vaccine Against Lyme for Outdoor Recreationists) clinical trial.
The announcement came at the end of a two-year trial conducted across sites in highly endemic areas of the United States, Canada, and Europe — the precise regions where 500,000 Americans are estimated to contract Lyme disease every year. The trial enrolled participants aged 5 and older and randomized them to receive four doses of either the vaccine or a saline placebo, given one dose each at months 0, 2, 5 to 9, and a booster one year after the third dose.
The pre-specified analyses showed 73.2 percent efficacy from 28 days post-dose 4 (Season 2) in reducing confirmed Lyme disease cases compared to placebo, and 74.8 percent efficacy from 1 day post-dose 4. Pfizer noted that while the pre-determined statistical criterion for the primary endpoint analysis was technically not met due to fewer-than-anticipated Lyme disease cases accruing over the study period, the confidence interval lower bound exceeded 20 percent in the second pre-specified analysis — a clinically meaningful threshold — providing sufficient confidence to proceed with regulatory submissions.
"Lyme disease can cause potentially serious consequences — where individuals and families face symptoms that can disrupt daily life, work, and long-term health — and there is currently no vaccine available," said Annaliesa Anderson, Ph.D., Senior Vice President and Chief Vaccines Officer at Pfizer. "The efficacy shown in the VALOR study of more than 70% is highly encouraging and creates confidence in the vaccine's potential to protect against this disease that can be debilitating."
What Makes This Vaccine Different — and Why Children Included Is Significant
PF-07307405 is a 6-valent OspA-based vaccine, meaning it contains outer surface protein A (OspA) antigens from six of the most clinically relevant Borrelia strains responsible for Lyme disease in North America and Europe. OspA is a surface protein expressed on Borrelia bacteria when they are in the tick gut — meaning the vaccine essentially intercepts the bacteria before they even leave the tick, by inducing antibodies that neutralize the pathogen while it is still inside the tick feeding on the vaccinated host's blood.
The original LYMErix vaccine, which was withdrawn from the market in 2002 following controversy over alleged side effects (which were never confirmed in rigorous studies), was also OspA-based but monovalent — meaning it targeted only one OspA serotype. The new vaccine's six-valent formulation is designed to provide broader coverage across the diverse Borrelia strains circulating in North America and Europe.
Critically, the vaccine has been tested and shown a favorable safety profile in participants as young as 5 years old — a population that is among the most active outdoors and among the highest-risk demographics for Lyme disease. Subject to positive ongoing data, Pfizer plans to submit a Biologics License Application (BLA) to the FDA and a Marketing Authorization Application (MAA) to the European Medicines Agency in 2026. If approved, PF-07307405 could reach the U.S. market in 2027, directly as the country's record-breaking tick season of 2026 is making its most urgent case for a preventive solution.
Frequently Asked Questions
Q: How effective is the new Lyme disease vaccine?
A: The Phase 3 VALOR trial showed 73.2–74.8% efficacy against confirmed Lyme disease cases in individuals aged 5 and older after completing the four-dose schedule.
Q: Is this vaccine available yet?
A: No. Pfizer plans to submit regulatory applications in 2026. FDA review and approval would likely bring availability to the U.S. market in 2027, pending approval.
Q: Why was the last Lyme disease vaccine withdrawn?
A: LYMErix was withdrawn in 2002 primarily for commercial reasons related to declining sales following public controversy over alleged side effects — concerns that were never confirmed by rigorous scientific studies.
Q: Who will the vaccine be recommended for?
A: The trial enrolled participants aged 5 and older. It is designed for people at increased risk due to residence in or outdoor activities in Lyme-endemic areas.
Q: How does an OspA-based Lyme vaccine work?
A: OspA (outer surface protein A) is expressed by Borrelia bacteria when they are in the tick gut. The vaccine induces antibodies that neutralize the bacteria while they are still inside the tick, before transmission to the human host.
