Pfizer and partner Valneva have removed about half of the participants from a large Phase 3 trial of their experimental Lyme disease vaccine following violations of study standards at some trial sites.
Pfizer and Valneva didn’t say what the specific violations were in a short statement Friday. But they indicated that sites run by a “third-party clinical trial site operator” had run afoul of certain ethics and scientific quality standards, compromising the integrity of the data being collected. The move wasn’t related to any safety concerns with the shot, known as VLA15, and wasn’t prompted by an adverse event, they said.
“Once Pfizer learned of potential violations … it conducted a thorough review of the operations and data collections at the clinical trial sites run by the third party and followed standard operating safeguards to determine the correct course of action,” the company said.
The disclosure adds new uncertainty to what is the largest trial of a vaccine for Lyme disease in decades.
According to Pfizer and Valneva, their shot is the only one in clinical development for the condition, which can be treated with antibiotics if caught early but causes significant health problems if not.
A vaccine, known as Lymerix and sold by GSK, was once available. But it was withdrawn in 2002 due to consumer complaints and low demand, and drugmakers have largely steered away from investing in another vaccine since, according to published reports.
Yet the prevalence of the bacterial infection, transferred to humans by tick bites, has grown in recent years, according to data from the Centers for Disease Control and Prevention. VLA15 could help curb those numbers and, so far, has produced encouraging results in Phase 2 testing. Pfizer began collaborating with Valneva on the shot in 2020 and would lead commercialization if it’s approved.
The two began their trial last August. The study enrolled participants at least five years of age in the U.S. and Europe, specifically in areas where Lyme disease is highly endemic. Enrollment was expected to be complete in the second quarter, Valneva said in a presentation last month.
The trial remains ongoing despite the setback, and the two companies plan to enroll more participants at its other study sites. They still aim to complete the study in time to seek regulatory approval in 2025, should the vaccine prove safe and effective.