Pfizer Inc (PFE) announced an update on their ongoing clinical study.
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The Phase 3 trial “A Phase 3, Multicenter, Placebo-Controlled, Randomized, Observer-Blinded Trial to Evaluate the Efficacy, Safety, Tolerability, Immunogenicity, and Lot Consistency of a 6-Valent OspA-Based Lyme Disease Vaccine in Healthy Participants ≥5 Years of Age” aims to test Pfizer’s VLA15 Lyme disease vaccine in people living in high-risk areas. It focuses on how well the vaccine prevents Lyme disease, how safe it is, and whether different batches perform the same.
The study tests VLA15, a six-strain Lyme disease vaccine given as a shot in the upper arm, against a saline placebo. The goal is to cut Lyme disease cases in the U.S. and Europe and show that all lots of the vaccine work and behave in a similar way.
The trial is interventional and Phase 3, with people randomly assigned to receive either VLA15 or placebo. It uses a parallel-group design and is “observer-blinded,” meaning participants, doctors, and outcome assessors do not know who gets the vaccine or placebo, and the main aim is disease prevention.
Participants receive three doses over several months, then a booster about a year later, timed around Lyme disease seasons. Some are followed for up to three Lyme seasons, allowing Pfizer and partner Valneva Austria GmbH to track how long protection may last and confirm safety over a longer period.
The study was first submitted on 5 July 2022, marking the formal start of regulatory tracking. The last update on 19 May 2026 shows the record remains active and refined as data mature and the trial status has moved to completed.
With the trial completed and an updated record, investors will watch closely for headline efficacy and safety data, which could support a new vaccine filing. A successful readout would add a new seasonal revenue stream for Pfizer (PFE), bolster its vaccine franchise post-COVID, and may increase competitive pressure on smaller Lyme-focused players and broader infectious disease names.
Regulatory milestones, such as a U.S. or European filing, could act as near-term catalysts for Pfizer’s stock if data are strong, while safety or efficacy concerns could weigh on sentiment. The study is now completed and recently updated, with further details available on the ClinicalTrials portal.
To learn more about PFE’s potential, visit the Pfizer Inc drug pipeline page.