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NCT Number: NCT07500506

A Study to Learn About the Safety, Tolerability, and Immunogenicity of a Fifth Dose of 6-Valent OspA-Based Lyme Disease Vaccine

The purpose of this study is to learn about the safety effects of the Lyme disease vaccine (called VLA15), and its ability to protect people from Lyme disease after a 5th dose of the vaccine.

This study is seeking participants who:

* are generally healthy and 7 years of age and older, * have already been vaccinated with 4 doses of VLA15 (from the VALOR study), and have blood sample taken post dose 4. * are not currently taking, or haven't recently taken, medicines like chemotherapy, blood products, or blood thinners. * are not pregnant or breastfeeding and do not plan to become pregnant while receiving the study vaccine.

All participants in this study will receive a total of 1 dose through a shot in the upper arm, either VLA15 or saline shot (saltwater).

The study will compare the experiences of people receiving the study vaccine or saltwater shot.

Participants will take part in this study for about 12 months. During this time, they will have 4 planned clinic visits. The clinic visits may include having a health check, giving a small amount of blood and getting the study vaccine or saltwater as a shot at the first visit.

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Key information

Conditions

Lyme Disease Bacterial Infections Bacterial Infections and Mycoses Borrelia Infections Gram-Negative Bacterial Infections Infections Spirochaetales Infections Tick-Borne Diseases Vector Borne Diseases

Age range

7 year and older

Sex eligibility

All sexes

Study type

Interventional

Phase

Phase 3

Primary location

Milestone Research Inc., London, Ontario, Canada

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About this study

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

Participants will be randomized in a 5:1 ratio to receive either one dose of VLA15 or placebo (saline) at the first visit. This study will use an external data monitoring committee (EDMC). The EDMC is independent of the Pfizer study team and includes only external members. The EDMC charter describes the role of the EDMC in more detail.

Approximately 1712 participants will be enrolled in the study.

Healthy individuals 7 years of age and older who have received 4 prior doses of active VLA15 from the C4601003 study, have a blood sample taken post dose 4, are willing to comply with all study procedures, and provide signed informed consent will be enrolled. Pregnant or breastfeeding individuals and fertile individuals who are unwilling or unable to use effective contraceptive methods as outlined in this protocol will not be enrolled. Individuals who have contraindication to vaccination, conditions or treatments that can inhibit the ability to mount an immune response to a vaccine, or other conditions that may increase the risk of study participation will be excluded from this study.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

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.

Treatment and study plan

VLA15

Biological

VLA15 injection IM

Placebo

Biological

Saline Injection

Primary outcomes

  1. Percentage of participants reporting prespecified local reactions

    Time frame: Within 7 days following each study intervention administration

  2. Percentage of participants reporting prespecified systemic events

    Time frame: Within 7 days following each study intervention administration

  3. Percentage of participants reporting adverse events (AEs)

    Time frame: Through 1 month following study intervention administration

  4. Percentage of participants reporting newly diagnosed chronic medical conditions (NDCMCs)

    Time frame: Through study completion, up to approximately 12 months.

  5. Percentage of participants reporting serious adverse events (SAEs)

    Time frame: Through study completion, up to approximately 12 months.

  6. Geometric mean ratio (GMR) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At 1 month after completion of Dose 5

    Objective to determine non-inferiority of Dose 5 compared to Dose 4 in all participants when there is a 1 year gap between Dose 4 and Dose 5.

  7. Sero-response of anti-OspA IgG concentrations for each serotype (ST1-ST6).

    Time frame: At 1 month after completion of Dose 5

    Difference in seroresponse rate between 1 month after Dose 5 and 1 month after Dose 4 for each serotype in all participants ≥7 years of age who received a fifth dose of VLA15 1 year after their fourth dose of VLA15.

Secondary outcomes

  1. Geometric mean ratio (GMR) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At 1 month after completion of Dose 5

    Objective to determine non-inferiority of Dose 5 compared to Dose 4 in adult participants when there is a 1 year gap between Dose 4 and Dose 5.

  2. Geometric mean ratio (GMR) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At 1 month after completion of Dose 5

    Objective to determine non-inferiority of Dose 5 compared to Dose 4 in all participants when there is a 2 year gap between Dose 4 and Dose 5.

  3. Geometric mean ratio (GMR) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At 1 month after completion of Dose 5

    Objective to describe the immune response following Dose 5 compared to Dose 4 in pediatric participants when there is a 1 year gap between Dose 4 and Dose 5.

  4. Geometric mean ratio (GMR) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At 1 month after completion of Dose 5

    Objective to describe the immune response following Dose 5 compared to Dose 4 in all participants (by age group) when there is a 2 year gap between Dose 4 and Dose 5.

  5. Geometric mean fold rise (GMFR) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At just prior to Dose 5 and 1 month after completion of Dose 5

    Objective to describe the immune response following Dose 5 compared to Dose 4 in all participants when there is a 1 or 2 year gap between Dose 4 and Dose 5.

  6. Geometric mean concentration (GMC) of anti-OspA IgG concentrations for each serotype (ST1-ST6)

    Time frame: At 1 month after completion of Dose 5

    Objective to describe the immune response following Dose 5 compared to Dose 4 in all participants when there is a 1 or 2 year gap between Dose 4 and Dose 5.

  7. Sero-response of anti-OspA IgG concentrations for each serotype (ST1-ST6).

    Time frame: At 1 month after completion of Dose 5

    Difference in seroresponse rate between 1 month after Dose 5 and 1 month after Dose 4 for each serotype in adult participants ≥18 years of age who received a fifth dose of VLA15 1 year after their fourth dose of VLA15.

  8. Sero-response of anti-OspA IgG concentrations for each serotype (ST1-ST6).

    Time frame: At 1 month after completion of Dose 5

    Difference in seroresponse rate between 1 month after Dose 5 and 1 month after Dose 4 for each serotype in all participants ≥7 years of age who received a fifth dose of VLA15 2 years after their fourth dose of VLA15.

  9. Sero-response of anti-OspA IgG concentrations for each serotype (ST1-ST6).

    Time frame: At 1 month after completion of Dose 5

    Seroresponse rate at 1 month after Dose 5 using pre-Dose 1 and pre-Dose 5 seroresponse rates as baseline in all participants who received a fifth dose of VLA15 1 year and 2 years after their fourth dose of VLA15.

Study contacts

Contact information is provided by the study sponsor or research team.

Pfizer CT.gov Call Center

CONTACT

[email protected]

1-800-718-1021

Sponsors and collaborators

Lead sponsor

Pfizer

Industry

Registry information

Official study title

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

Important dates

Study start
2026
Primary completion
2026
Study completion
2026
First posted
Mar 30, 2026
Registry last updated
May 6, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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