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Fifth dose of the 6‑valent OspA Lyme vaccine (VLA15)

A PHASE 3, RANDOMIZED, PLACEBO-CONTROLLED, DOUBLE-BLINDED STUDY TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF A FIFTH DOSE OF 6-VALENT OSPA-BASED LYME DISEASE VACCINE, VLA15, IN HEALTHY PARTICIPANTS ≥7 YEARS OF AGE

Phase 3 Interventional Pfizer · NCT07500506

This test gives a fifth dose of the VLA15 Lyme vaccine to people age 7 and older who already got four doses to see if it is safe and boosts immune protection.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment1712 (estimated)
Ages7 Years and up
SexAll
SponsorPfizer Industry-sponsored
Drugs / interventionschemotherapy
Locations22 sites (Bangor, Maine and 21 other locations)
Trial IDNCT07500506 on ClinicalTrials.gov

What this trial studies

This is a randomized, double‑blind, placebo‑controlled Phase 3 trial that enrolls about 1,712 healthy participants aged 7 years and older who previously received four doses of VLA15. Participants are randomized 5:1 to receive a single injection of VLA15 or saline placebo at the first visit, with safety, tolerability, and immune responses followed over about 12 months. Study visits include collection of blood samples (including a required post‑dose‑4 sample from the prior study), physical exams, and safety monitoring across four planned clinic visits. An independent external data monitoring committee (EDMC) provides oversight of participant safety during the trial.

Who should consider this trial

Good fit: Healthy individuals age 7 and older who have already received four prior doses of VLA15 in the referenced study and have a post‑dose‑4 blood sample available, are willing to follow study procedures, and are not pregnant or breastfeeding are ideal candidates.

Not a fit: People who have not received the prior four VLA15 doses, are pregnant or breastfeeding, or who have conditions or treatments that blunt vaccine responses (for example certain immunodeficiencies or recent immunosuppressive therapy) are unlikely to be eligible or to benefit from this booster.

Why it matters

Potential benefit: If successful, the fifth dose could boost and prolong immune protection against Lyme disease for people who already completed the initial VLA15 series.

How similar studies have performed: Earlier Phase 1/2 trials of VLA15 and other OspA‑based Lyme vaccine candidates showed acceptable safety and induced immune responses, and this trial builds on those results.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* Participants who are healthy as determined by medical history and clinical judgment.
* Participants willing and able to comply with all scheduled visits, IP receipt, and other procedures throughout the study.
* Able to provide Informed Consent.
* Participants must have received 4 doses of VLA15 in the C4601003 study, and have a V7 blood sample available.

Exclusion Criteria:

* Pregnant or breastfeeding participants.
* Allergies or contraindications to vaccines or their components.
* Health issues including: blood clotting deficiencies, immunodeficiencies, bone marrow disorder, or uncontrolled psychiatric conditions.
* Receipt of therapies to treat malignancies, blood/plasma products and immunoglobulins, systemic corticosteroids and immunosuppressants, or anticoagulant therapy in recent medical history.
* Recent or concurrent participation in a separate interventional study.
* Staff or direct family of the study site staff and Sponsor.

Where this trial is running

Bangor, Maine and 21 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
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Conditions Lyme Disease
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.