Lyme BorreliosisPhase 2NCT04801420

Phase 2 Study Of VLA15, A Vaccine Candidate Against Lyme Borreliosis, In A Healthy Pediatric And Adult Study Population

A Phase 2 study testing VLA15 in people with Lyme Borreliosis, run by Pfizer at 19 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record

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Trial summary

Who is it for?: Ages 5 to 65 yearsHealthy volunteers can take part
Conditions the study is for: Lyme Borreliosis
What is being tested?: VLA15
Type of treatment: Vaccines
Could I receive a placebo?: Yes, some participants may receive a placebo
How many people: 625 participants
Where: 19 sitesUnited States
Study dates: 8 Mar 2021to 2 Jul 2025
Phase: Phase 2
Are there results?: Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 5 to 65 years
All sexes
Healthy volunteers accepted
Child, Adult, Older adult

Who may be able to join

Subject is aged 5 to 65 years at the day of screening (Visit 0)
Subject is of good general health
Parent(s)/legal representative(s) and subject understand the study and its procedures, agree to its provisions
for subjects aged 18-65 years: written informed consent prior to any study related procedures
for subjects aged 5-17 years: written informed consent by the subject's legal representative(s), according to local requirements, and written informed assent of the subject, if applicable, prior to any study related procedures.
If subject is of childbearing potential: Subject has a negative serum pregnancy test at screening (Visit 0) and agrees to employ adequate birth control measures according to following timelines:

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Main Study Phase: duration of entire study
Booster Phase: until 5 months after each booster vaccination (Booster 1 until Month 23, Booster 2 until Month 35 and Booster 3 until Month 47)
Subject is willing and able to comply with scheduled visits, treatment plan, and other study procedures
Subject is available for the duration of the study and can be contacted by telephone during study participation

Who cannot join

Subject has a chronic illness related to Lyme borreliosis (LB), an active symptomatic LB, or received treatment for LB within the last 3 months prior to Day 1;
Subject received previous vaccination against LB;
Subject had a tick bite within 4 weeks prior to Day 1;
Subject has a medical history of or currently has a clinically relevant disease;
Subject has a medical history of or currently has a neuro- inflammatory or autoimmune disease;
Subject has a known thrombocytopenia, bleeding disorder, or received anticoagulants in the 3 weeks prior to Day 1;

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Subject has received an active or passive immunization within 4 weeks prior to Day 1;
Subject has received any other registered or non-registered medicinal product in another clinical trial within 4 weeks prior to vaccination at Day 1;
Subject has a known or suspected defect of the immune system or received immuno-suppressive therapy within 4 weeks prior to Day 1;
Subject has a history of anaphylaxis of unknown cause or severe allergic reactions of unknown cause or has a known hypersensitivity or allergic reactions to one of the components of the vaccine;
Subject had any malignancy in the past 5 years;
Subject is pregnant, has plans to become pregnant during the course of the study or is lactating at the time of enrollment;
Subject has donated or plans to donate blood or blood-derived products 4 weeks prior to Day 1;
Subject has any condition that may compromise its well-being, might interfere with evaluation of study endpoints, or would limit the subject's ability to complete the study;
Subject is in a dependent relationship with the sponsor/investigator

Trial locations and contacts

19 sites in 1 country.

City, postcode or hospital

19 sites in 1 country

United States19 sites

Meridian Clinical Research LLC
Binghamton, New York, 13905
New England Research Associates
Bridgeport, Connecticut, 06606
Velocity Clinical Research, Inc.
Cleveland, Ohio, 44122
Foundation Pediatrics
East Orange, New Jersey, 07018
Allegheny Health and Wellness Pavilion
Erie, Pennsylvania, 16506
Liberty Family Practice
Erie, Pennsylvania, 16508
Lockman & Lubell Pediatric Associates
Fort Washington, Pennsylvania, 19034
Med Clinical Research Partners, LLC
Irvington, New Jersey, 07111
Clinical Research Institute, Inc.
Minneapolis, Minnesota, 55402
Hasbro Children's Hospital
Providence, Rhode Island, 02903
Rhode Island Hospital
Providence, Rhode Island, 02903
The Miriam Hospital
Providence, Rhode Island, 02906
Rochester Clinical Research, Inc.
Rochester, New York, 14609
Stamford Therapeutics Consortium
Stamford, Connecticut, 06905
Richmond Behavioral Associates
Staten Island, New York, 10314
Advantage Clinical Trials
The Bronx, New York, 10467
Velocity Clinical Research Providence
Warwick, Rhode Island, 02886
Chase Medical Research, LLC
Waterbury, Connecticut, 06708
Pediatric Associates of Conn. PC
Waterbury, Connecticut, 06708

Other trials in United States

About this study

Official title: SAFETY AND IMMUNOGENICITY STUDY OF VLA15, A MULTIVALENT RECOMBINANT OSPA BASED VACCINE CANDIDATE AGAINST LYME BORRELIOSIS: A RANDOMIZED, CONTROLLED, OBSERVER-BLIND PHASE 2 STUDY IN A HEALTHY PEDIATRIC AND ADULT STUDY POPULATION

VLA15-221 is a Phase 2 study, which will be conducted in two parts: Main Study Phase (Part A) and Booster Phase (Part B). The study will compare the safety and immunogenicity of two different primary immunization schedules applying three (Month 0-2-6) or two (Month 0- 6) vaccinations. Within the study, 600 healthy subjects aged 5-65 years will be included. Subjects with a history of Lyme borreliosis (previous infection with Borrelia) as well as Borrelia naïve subjects will be enrolled. Study duration per subject will be a maximum of 50 months per subject.

Read the detailed description

VLA15-221 is a randomized, observer-blind, placebo controlled, multicenter Phase 2 study, which is set up in two parts: Main Study Phase (Part A) and Booster Phase (Part B). In Part A 600 subjects aged 5-65 years will be enrolled 1:1:1 into three groups: Group 1 will be vaccinated with VLA15 at Month 0-2-6, Group 2 will be vaccinated with VLA15 at Month 0-6 and with placebo at Month 2 and Group 3 will be vaccinated with placebo at Month 0-2-6. In Part B all eligible subjects will receive booster injections with VLA15 or placebo at Month 18, 30 and 42.

Conditions: Lyme Borreliosis
Being tested: VLA15, Placebo
Keywords: VLA15, Lyme Borreliosis, Vaccine, Lyme disease, Borrelia
Medical subject headings: Lyme Disease

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

VLA15Biological
a multivalent recombinant Outer Surface Protein A (OspA) based vaccine candidate
PlaceboBiological
PBS (Phosphate Buffered Saline)

Study groups in NCT04801420
Study group	Role	What they receive
Part A+B - Group 1	Experimental	Part A: VLA15 at Month 0, 2 and 6 Part B: VLA15 at Month 18, 30 and 42 Receives: Biological: VLA15
Part A+B - Group 2	Experimental	Part A: VLA15 at Month 0 and 6, placebo at Month 2 Part B: VLA15 at Month 18, 30 and 42 Receives: Biological: VLA15; Biological: Placebo
Part A+B - Group 3	Placebo comparator	Part A: Placebo at Month 0, 2 and 6 Part B: Placebo at Month 18, 30 and 42 Receives: Biological: Placebo

What is being measured

The primary outcome is the main question the study is designed to answer.

Percentage of Participants With Solicited Local and Solicited Systemic Adverse Events (AEs) Within 7 Days After Vaccination 1
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness meeting grading scale (MGS), swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after vaccination 1 at Month 0
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 2
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after vaccination 2 at Month 2
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 3
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after vaccination 3 at Month 6
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Any Vaccination During the Main Study Phase
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after any vaccination 1, 2 or 3 at Month 0, 2 and 6, respectively
Geometric Mean Titers (GMTs) for Immunoglobulin G (IgG) Against Each Outer Surface Protein A (OspA) Serotype (ST1 to ST6) at Day 208 During the Main Study Phase
GMTs for IgG against each OspA serotype ST1 to ST6, determined by an IgG binding assay at Day 208 was presented in this outcome measure.
Measured: At Day 208 (Month 7)

Secondary outcomes (19)

Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 1 Booster Dose
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after vaccination 1 booster dose at Month 18
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 2 Booster Dose
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after vaccination 2 booster dose at Month 30
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 3 Booster Dose
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Measured: From Day 1 to Day 7 after vaccination 3 booster dose at Month 42
Percentage of Participants With Serious Adverse Events (SAEs)
A SAE was any untoward medical occurrence that at any dose: resulted in death; required inpatient hospitalization or prolongation of existing hospitalization; was life-threatening; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect; was another medically important condition.
Measured: From Day 1 of vaccination 1 up to 6 months following the last booster dose (up to Month 48)
Percentage of Participants With Adverse Events of Special Interest (AESIs)
An AESI (serious or non-serious) was one of scientific and medical concern specific to the sponsor's product or program, for which ongoing monitoring and rapid communication by the investigator to the sponsor were appropriate.
Measured: From Day 1 of vaccination 1 up to 6 months following the last booster dose (up to Month 48)
Percentage of Participants With Unsolicited AE
An AE was any untoward medical occurrence in a participant administered an investigational product, whether or not related to this treatment. Unsolicited AEs were defined as any solicited local or systemic AE if it had an onset date more than 6 days after vaccination or any other symptom or untoward medical event.
Measured: Up to 28 Days after vaccination 1, 2 or 3 at Month 0, 2 and 6, respectively, and up to 28 Days after vaccination 1, 2 or 3 booster dose at Month 18, 30 and 42, respectively
Percentage of Participants With SAEs, AESIs, Solicited and Unsolicited AEs Stratified by Age Group
Percentage of participants with SAEs, AESIs, solicited and unsolicited AEs stratified by age group 5-11, 12-17 and 18-65 years were reported. SAE: any untoward medical occurrence that at any dose: resulted in death; required inpatient hospitalization or prolongation of existing hospitalization; was life-threatening; resulted in persistent or significant disability/incapacity; was a congenital anomaly/birth defect; was another medically important condition. AESI: scientific and medical concern specific to the sponsor's product or program. Solicited AE: predefined reactions at injection site or systemic reactions after each vaccination. Unsolicited AEs: any solicited local or systemic AE if it had an onset date more than 6 days after vaccination or any other symptom or untoward medical event.
Measured: SAEs & AESIs: From Day 1 of vaccination up to Month 48; Solicited AEs: from Day 1 to Day 7 after vaccination 1, 2, 3, 4, 5 and 6; Unsolicited AEs: up to 28 Days after vaccination 1, 2, 3, 4, 5 and 6
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) at Baseline, Days 85, 180, 365 and Month 18
GMTs for IgG against each OspA serotype ST1 to ST6, determined by an IgG binding assay were evaluated.
Measured: Baseline; Days 85, 180 and 365; Month 18
Seroconversion Rate (SCR) at Days 85, 180, 208, 365 and Month 18
Seroconversion for enzyme linked immunosorbent assay (ELISA) was defined as a change from seronegative at baseline to seropositive at a measured time point. For participants who were OspA seropositive at baseline, seroconversion was defined as a greater than or equal to (>=) 4-fold rise in IgG antibody titer from baseline. SCR was percentage of participants with seroconversion reported for each OspA serotype specific IgG ST1 to ST6, as determined by ELISA.
Measured: Days 85, 180, 208 and 365; Month 18
Geometric Mean of the Fold Rise (GMFR) for IgG When Compared to Baseline Against Each OspA Serotype (ST1 to ST6) at Days 85 and 208
GMFR for IgG when compared to baseline against each OspA serotype ST1 to ST6, determined by IgG binding assay at Day 85 and Day 208 were evaluated.
Measured: Days 85 and 208
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Baseline, Days 85, 180, 194, 365 and Month 18
GMTs for IgG against each OspA serotype ST1 to ST6, determined by an IgG binding assay stratified by age group (5-11, 12-17 and 18-65 years) were evaluated. Day 194 data was reported for adult participants only as pre-specified in protocol.
Measured: Baseline; Days 85, 180, 194 (18 to 65 years only) and 365; Month 18
SCR Stratified by Age Group at Days 85, 180, 194, 208, 365 and Month 18
Seroconversion for ELISA was defined as a change from seronegative at baseline to seropositive at a measured time point. For participants who were OspA seropositive at baseline, seroconversion was defined as a >=4-fold rise in IgG antibody titer from baseline. SCR was percentage of participants with seroconversion reported for each OspA serotype specific IgG ST1 to ST6, as determined by ELISA. Day 194 data was reported for adult participants only as pre-specified in protocol.
Measured: Days 85, 180, 194 (18 to 65 years only), 208 and 365; Month 18
GMFR for IgG When Compared to Baseline Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Days 85 and 208
GMFR for IgG when compared to baseline against each OspA serotype ST1 to ST6, stratified by age group (5-11, 12-17 and 18-65 years) determined by IgG binding assay at Day 85 and Day 208 were evaluated.
Measured: Days 85 and 208
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
GMTs for IgG against each OspA serotype ST1 to ST6, determined by an IgG binding assay were evaluated.
Measured: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
SCR at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
Seroconversion for ELISA was defined as a change from seronegative at baseline to seropositive at a measured time point. For participants who were OspA seropositive at baseline, seroconversion was defined as a >=4-fold rise in IgG antibody titer from baseline. SCR was percentage of participants with seroconversion reported for each OspA serotype specific IgG ST1 to ST6, as determined by ELISA.
Measured: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
GMFR for IgG Against Each OspA Serotype (ST1 to ST6) at Months 19, 31 and 43 During the Booster Phase
GMFRs for IgG were determined by IgG binding assay for each OspA serotype (ST1-ST6) at Months 19, 31, and 43 relative to the corresponding pre-booster timepoints Months 18, 30, and 42, respectively.
Measured: Months 19, 31 and 43
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
GMTs for IgG against each OspA serotype ST1 to ST6, determined by an IgG binding assay stratified by age group (5-11, 12-17 and 18-65 years) were evaluated.
Measured: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
SCR Stratified by Age Group at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
Seroconversion for ELISA was defined as a change from seronegative at baseline to seropositive at a measured time point. For participants who were OspA seropositive at baseline, seroconversion was defined as a >=4-fold rise in IgG antibody titer from baseline. SCR was percentage of participants with seroconversion reported for each OspA serotype specific IgG ST1 to ST6, as determined by ELISA.
Measured: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
GMFR for IgG Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Months 19, 31 and 43 During the Booster Phase
GMFRs for IgG were determined by IgG binding assay for each OspA serotype (ST1-ST6), stratified by age group (5-11, 12-17 and 18-65 years) at Months 19, 31, and 43 relative to the corresponding pre-booster timepoints Months 18, 30, and 42, respectively.
Measured: Months 19, 31 and 43

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

8 Mar 20212 Jul 2025

First posted17 Mar 2021
Study start8 Mar 2021
Primary completion25 Mar 2022
Study completion2 Jul 2025

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (3)Papers the sponsor has linked to this study.
Other trials for Lyme BorreliosisStudies of the same condition, open and under way.
More trials run by PfizerThe sponsor's other registered studies.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 2
Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Quadruple blind
Who is masked: Participant, Care provider, Investigator, Outcomes assessor
Enrolment: 625 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04801420
Sponsor's protocol ID: VLA15-221
Other IDs: C4601008
Status last verified: Aug 2026
First submitted: 8 Mar 2021
Last updated: 15 Sep 2026
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

Publications

Wagner L, Kadlecek V, Skaroupkova J, Scharnagl N, Hochreiter R, Messier M, Jaramillo JC, Larcher-Steiner J, Hegele L, Lamberth E, Murphy T, Maguire JD, Clarkin C, Derhaschnig U, Eder-Lingelbach S. A second yearly booster dose of the VLA15 Lyme borreliosis vaccine candidate in healthy individuals. Nat Commun. 2026 Aug 4;17(1):9386. doi: 10.1038/s41467-026-75871-3.
PubMed 42680745
Wagner L, Obersriebnig M, Hochreiter R, Kadlecek V, Larcher-Senn J, Hegele L, Maguire JD, Murphy T, Derhaschnig U, Bezay N, Jaramillo JC, Eder-Lingelbach S, Messier M. Immunogenicity and safety of an 18-month booster dose of the VLA15 Lyme borreliosis vaccine candidate after primary immunisation in children, adolescents, and adults in the USA: a randomised, observer-blind, placebo-controlled, phase 2 trial. Lancet Infect Dis. 2026 Mar;26(3):314-328. doi: 10.1016/S1473-3099(25)00541-9. Epub 2025 Nov 7.
PubMed 41213278
Wagner L, Obersriebnig M, Kadlecek V, Hochreiter R, Ghadge SK, Larcher-Senn J, Hegele L, Maguire JD, Derhaschnig U, Jaramillo JC, Eder-Lingelbach S, Bezay N. Immunogenicity and safety of different immunisation schedules of the VLA15 Lyme borreliosis vaccine candidate in adults, adolescents, and children: a randomised, observer-blind, placebo-controlled, phase 2 trial. Lancet Infect Dis. 2025 Sep;25(9):986-999. doi: 10.1016/S1473-3099(25)00092-1. Epub 2025 Apr 25.
PubMed 40294611

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 15 Sep 2026. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: SAFETY AND IMMUNOGENICITY STUDY OF VLA15, A MULTIVALENT RECOMBINANT OSPA BASED VACCINE CANDIDATE AGAINST LYME BORRELIOSIS: A RANDOMIZED, CONTROLLED, OBSERVER-BLIND PHASE 2 STUDY IN A HEALTHY PEDIATRIC AND ADULT STUDY POPULATION
ClinicalTrials.gov ID: NCT04801420
Acronym / sponsor ID: VLA15-221
Conditions: Lyme Borreliosis
Keywords: VLA15, Lyme Borreliosis, Vaccine, Lyme disease, Borrelia
Phase: Phase 2
Study type: Interventional
Recruitment status: Completed
Enrolment: 625 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Collaborators: Valneva Austria GmbH
Study start: 8 Mar 2021 (actual)
Primary completion: 25 Mar 2022 (actual)
Study completion: 2 Jul 2025 (actual)
First posted: 17 Mar 2021 (actual)
Results: Posted 7 Jun 2023

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Detailed description

Study design

Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Quadruple blind (participant, care provider, investigator, outcomes assessor)
Number of arms: 3

Arm	Type	Receives
Part A+B - Group 1	Experimental	Biological: VLA15Part A: VLA15 at Month 0, 2 and 6 Part B: VLA15 at Month 18, 30 and 42
Part A+B - Group 2	Experimental	Biological: VLA15, Biological: PlaceboPart A: VLA15 at Month 0 and 6, placebo at Month 2 Part B: VLA15 at Month 18, 30 and 42
Part A+B - Group 3	Placebo comparator	Biological: PlaceboPart A: Placebo at Month 0, 2 and 6 Part B: Placebo at Month 18, 30 and 42

Who may qualify

Ages: 5 to 65 years
Sex: All
Healthy volunteers: Accepted
Age groups: Child, Adult, Older adult

Key inclusion criteria (10 listed)

Subject is aged 5 to 65 years at the day of screening (Visit 0)
Subject is of good general health
Parent(s)/legal representative(s) and subject understand the study and its procedures, agree to its provisions
If subject is of childbearing potential: Subject has a negative serum pregnancy test at screening (Visit 0) and agrees to employ adequate birth control measures according to following timelines:
Subject is willing and able to comply with scheduled visits, treatment plan, and other study procedures

Key exclusion criteria (15 listed)

Subject has a chronic illness related to Lyme borreliosis (LB), an active symptomatic LB, or received treatment for LB within the last 3 months prior to Day 1;
Subject received previous vaccination against LB;
Subject had a tick bite within 4 weeks prior to Day 1;
Subject has a medical history of or currently has a clinically relevant disease;
Subject has a medical history of or currently has a neuro- inflammatory or autoimmune disease;

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
VLA15a multivalent recombinant Outer Surface Protein A (OspA) based vaccine candidate	Biological	Part A+B - Group 1, Part A+B - Group 2
PlaceboPBS (Phosphate Buffered Saline)	Biological	Part A+B - Group 2, Part A+B - Group 3

Primary outcome

Percentage of Participants With Solicited Local and Solicited Systemic Adverse Events (AEs) Within 7 Days After Vaccination 1
Time frame: From Day 1 to Day 7 after vaccination 1 at Month 0
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness meeting grading scale (MGS), swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 2
Time frame: From Day 1 to Day 7 after vaccination 2 at Month 2
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 3
Time frame: From Day 1 to Day 7 after vaccination 3 at Month 6
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Any Vaccination During the Main Study Phase
Time frame: From Day 1 to Day 7 after any vaccination 1, 2 or 3 at Month 0, 2 and 6, respectively
Participants or their legal guardians were required to record any solicited local and systemic AEs in the electronic diary. Solicited symptoms were pre-defined symptoms which were collected via an electronic diary. Solicited local AEs included pain, tenderness, erythema/redness MGS, swelling MGS and induration/hardening MGS. Solicited systemic AEs included headache, muscle pain, joint pain, nausea, vomiting, fatigue and fever.
Geometric Mean Titers (GMTs) for Immunoglobulin G (IgG) Against Each Outer Surface Protein A (OspA) Serotype (ST1 to ST6) at Day 208 During the Main Study Phase
Time frame: At Day 208 (Month 7)
GMTs for IgG against each OspA serotype ST1 to ST6, determined by an IgG binding assay at Day 208 was presented in this outcome measure.

19 secondary outcomes

Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 1 Booster Dose
Time frame: From Day 1 to Day 7 after vaccination 1 booster dose at Month 18
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 2 Booster Dose
Time frame: From Day 1 to Day 7 after vaccination 2 booster dose at Month 30
Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 3 Booster Dose
Time frame: From Day 1 to Day 7 after vaccination 3 booster dose at Month 42
Percentage of Participants With Serious Adverse Events (SAEs)
Time frame: From Day 1 of vaccination 1 up to 6 months following the last booster dose (up to Month 48)
Percentage of Participants With Adverse Events of Special Interest (AESIs)
Time frame: From Day 1 of vaccination 1 up to 6 months following the last booster dose (up to Month 48)
Percentage of Participants With Unsolicited AE
Time frame: Up to 28 Days after vaccination 1, 2 or 3 at Month 0, 2 and 6, respectively, and up to 28 Days after vaccination 1, 2 or 3 booster dose at Month 18, 30 and 42, respectively
Percentage of Participants With SAEs, AESIs, Solicited and Unsolicited AEs Stratified by Age Group
Time frame: SAEs & AESIs: From Day 1 of vaccination up to Month 48; Solicited AEs: from Day 1 to Day 7 after vaccination 1, 2, 3, 4, 5 and 6; Unsolicited AEs: up to 28 Days after vaccination 1, 2, 3, 4, 5 and 6
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) at Baseline, Days 85, 180, 365 and Month 18
Time frame: Baseline; Days 85, 180 and 365; Month 18
Seroconversion Rate (SCR) at Days 85, 180, 208, 365 and Month 18
Time frame: Days 85, 180, 208 and 365; Month 18
Geometric Mean of the Fold Rise (GMFR) for IgG When Compared to Baseline Against Each OspA Serotype (ST1 to ST6) at Days 85 and 208
Time frame: Days 85 and 208
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Baseline, Days 85, 180, 194, 365 and Month 18
Time frame: Baseline; Days 85, 180, 194 (18 to 65 years only) and 365; Month 18
SCR Stratified by Age Group at Days 85, 180, 194, 208, 365 and Month 18
Time frame: Days 85, 180, 194 (18 to 65 years only), 208 and 365; Month 18
GMFR for IgG When Compared to Baseline Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Days 85 and 208
Time frame: Days 85 and 208
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
Time frame: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
SCR at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
Time frame: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
GMFR for IgG Against Each OspA Serotype (ST1 to ST6) at Months 19, 31 and 43 During the Booster Phase
Time frame: Months 19, 31 and 43
GMTs for IgG Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
Time frame: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
SCR Stratified by Age Group at Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
Time frame: Months 18, 19, 23, 26, 30, 31, 39, 42, 43 and 48
GMFR for IgG Against Each OspA Serotype (ST1 to ST6) Stratified by Age Group at Months 19, 31 and 43 During the Booster Phase
Time frame: Months 19, 31 and 43

Results and safety

Results posted to the registry on 7 Jun 2023, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
Group 1: VLA15	208	128
Group 2: VLA15 + Placebo	209	118
Group 3: Placebo	208	113

Primary outcome: Percentage of Participants With Solicited Local and Solicited Systemic Adverse Events (AEs) Within 7 Days After Vaccination 1

Time frame: From Day 1 to Day 7 after vaccination 1 at Month 0. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	Group 1: VLA15 n = 127	Group 2: VLA15 + Placebo n = 112	Group 3: Placebo n = 206	Received Any VLA15 Including Wrong/Missed Vaccination n = 419	All Participants n = 625
Pain	61.0 (52.1 to 69.1)	52.8 (43.4 to 61.9)	12.6 (8.7 to 17.9)	60.3 (55.4 to 65.0)	44.5 (40.6 to 48.5)
Tenderness	80.5 (72.6 to 86.5)	80.7 (72.3 to 87.0)	19.6 (14.7 to 25.7)	81.6 (77.5 to 85.0)	61.2 (57.3 to 65.0)
Erythema/Redness MGS	10.0 (5.8 to 16.7)	10.1 (5.7 to 17.2)	2.5 (1.1 to 5.8)	13.1 (10.1 to 16.7)	9.6 (7.5 to 12.2)
Swelling MGS	5.9 (2.9 to 11.6)	4.6 (2.0 to 10.3)	0.5 (0.1 to 2.8)	9.1 (6.7 to 12.4)	6.2 (4.6 to 8.5)
Induration/Hardening MGS	9.2 (5.2 to 15.8)	3.7 (1.4 to 9.1)	1.0 (0.3 to 3.6)	8.8 (6.4 to 12.0)	6.2 (4.6 to 8.5)
Headache	27.3 (20.1 to 35.8)	23.1 (16.2 to 31.9)	19.6 (14.7 to 25.7)	23.4 (19.5 to 27.8)	22.1 (19.0 to 25.7)
Muscle pain	36.4 (28.3 to 45.2)	33.0 (24.9 to 42.3)	11.1 (7.4 to 16.2)	35.6 (31.0 to 40.4)	27.5 (24.0 to 31.2)
Joint pain	10.7 (6.4 to 17.5)	3.7 (1.4 to 9.1)	6.0 (3.5 to 10.2)	7.8 (5.6 to 10.9)	7.2 (5.4 to 9.6)

Population analysed: Safety analysis set (SAS) included all participants who entered into the study and received at least one vaccination. Participants were analyzed according to the actual treatment received. Here, all participants reported under "Overall Number of Participants Analyzed" contributed data to the table but may not have evaluable data for every row and "Number Analyzed" signifies number of participants evaluable for the specified rows.

Primary outcome: Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 2

Time frame: From Day 1 to Day 7 after vaccination 2 at Month 2. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	Group 1: VLA15 n = 127	Group 2: VLA15 + Placebo n = 112	Group 3: Placebo n = 206	Received Any VLA15 Including Wrong/Missed Vaccination n = 419	All Participants n = 625
Pain	55.6 (46.9 to 64.1)	4.8 (2.1 to 10.7)	8.5 (5.3 to 13.3)	31.9 (27.5 to 36.7)	24.3 (21.0 to 27.9)
Tenderness	81.0 (73.2 to 86.9)	9.5 (5.3 to 16.6)	14.7 (10.3 to 20.4)	47.3 (42.5 to 52.3)	36.7 (32.9 to 40.7)
Erythema/Redness MGS	16.3 (10.8 to 23.8)	0.0 (0.0 to 3.5)	1.6 (0.5 to 4.6)	7.4 (5.2 to 10.5)	5.5 (3.9 to 7.7)
Swelling MGS	13.8 (8.8 to 21.0)	0.0 (0.0 to 3.5)	0.5 (0.1 to 2.9)	5.4 (3.6 to 8.1)	3.8 (2.5 to 5.7)
Induration/Hardening MGS	12.1 (7.5 to 19.0)	0.0 (0.0 to 3.5)	0.0 (0.0 to 2.0)	5.4 (3.5 to 8.1)	3.6 (2.4 to 5.5)
Headache	20.3 (14.2 to 28.3)	10.6 (6.0 to 18.0)	12.6 (8.6 to 18.1)	15.5 (12.2 to 19.4)	14.5 (11.9 to 17.6)
Muscle pain	25.8 (18.9 to 34.2)	3.8 (1.5 to 9.5)	3.7 (1.8 to 7.4)	14.1 (11.0 to 17.9)	10.7 (8.4 to 13.5)
Joint pain	4.9 (2.3 to 10.2)	2.9 (1.0 to 8.1)	1.6 (0.5 to 4.6)	4.6 (3.0 to 7.2)	3.6 (2.4 to 5.5)

Population analysed: SAS included all participants who entered into the study and received at least one vaccination. Participants were analyzed according to the actual treatment received. Here, all participants reported under "Overall Number of Participants Analyzed" contributed data to the table but may not have evaluable data for every row and "Number Analyzed" signifies number of participants evaluable for the specified rows.

Primary outcome: Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Vaccination 3

Time frame: From Day 1 to Day 7 after vaccination 3 at Month 6. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	Group 1: VLA15 n = 127	Group 2: VLA15 + Placebo n = 112	Group 3: Placebo n = 206	Received Any VLA15 Including Wrong/Missed Vaccination n = 419	All Participants n = 625
Pain	57.5 (48.6 to 66.0)	60.0 (50.4 to 68.9)	5.6 (3.1 to 10.1)	59.2 (54.1 to 64.1)	41.7 (37.6 to 45.9)
Tenderness	73.6 (65.1 to 80.6)	82.1 (73.7 to 88.2)	13.0 (8.8 to 18.7)	78.2 (73.7 to 82.1)	57.0 (52.8 to 61.1)
Erythema/Redness MGS	11.7 (7.1 to 18.6)	7.5 (3.9 to 14.2)	1.1 (0.3 to 4.0)	9.6 (7.0 to 13.1)	6.8 (5.0 to 9.3)
Swelling MGS	8.4 (4.6 to 14.8)	11.3 (6.6 to 18.8)	0.6 (0.1 to 3.1)	9.1 (6.5 to 12.5)	6.3 (4.5 to 8.7)
Induration/Hardening MGS	8.4 (4.6 to 14.8)	6.6 (3.2 to 13.0)	0.6 (0.1 to 3.1)	8.2 (5.8 to 11.5)	5.7 (4.1 to 8.0)
Headache	15.4 (10.0 to 23.0)	18.9 (12.6 to 27.4)	9.0 (5.6 to 14.1)	18.5 (14.8 to 22.8)	15.4 (12.6 to 18.7)
Muscle pain	27.1 (19.9 to 35.8)	29.2 (21.4 to 38.5)	7.3 (4.3 to 12.2)	28.3 (23.9 to 33.1)	21.4 (18.2 to 25.1)
Joint pain	8.5 (4.7 to 15.0)	2.8 (1.0 to 8.0)	3.4 (1.6 to 7.2)	5.0 (3.2 to 7.7)	4.4 (3.0 to 6.5)

Primary outcome: Percentage of Participants With Solicited Local and Solicited Systemic AEs Within 7 Days After Any Vaccination During the Main Study Phase

Time frame: From Day 1 to Day 7 after any vaccination 1, 2 or 3 at Month 0, 2 and 6, respectively. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	Group 1: VLA15 n = 190	Group 2: VLA15 + Placebo n = 187	Group 3: Placebo n = 208	Received Any VLA15 Including Wrong/Missed Vaccination n = 417	All Participants n = 625
Pain	80.5 (74.3 to 85.5)	77.0 (70.5 to 82.5)	16.8 (12.4 to 22.5)	77.0 (72.7 to 80.8)	57.0 (53.0 to 60.8)
Tenderness	92.6 (88.0 to 95.6)	92.5 (87.8 to 95.5)	28.4 (22.7 to 34.8)	90.6 (87.5 to 93.1)	69.9 (66.2 to 73.4)
Erythema/ Redness MGS	26.8 (21.0 to 33.6)	18.7 (13.8 to 24.9)	3.4 (1.6 to 6.8)	21.8 (18.1 to 26.0)	15.7 (13.0 to 18.7)
Swelling MGS	20.5 (15.4 to 26.8)	16.6 (11.9 to 22.6)	1.4 (0.5 to 4.2)	18.0 (14.6 to 22.0)	12.5 (10.1 to 15.3)
Induration/ Hardening MGS	19.5 (14.5 to 25.7)	14.4 (10.1 to 20.2)	1.4 (0.5 to 4.2)	16.5 (13.3 to 20.4)	11.5 (9.2 to 14.3)
Headache	38.4 (31.8 to 45.5)	36.4 (29.8 to 43.5)	28.8 (23.1 to 35.3)	37.4 (32.9 to 42.1)	34.6 (30.9 to 38.4)
Muscle pain	45.8 (38.9 to 52.9)	48.1 (41.1 to 55.3)	17.8 (13.2 to 23.6)	46.8 (42.0 to 51.6)	37.1 (33.4 to 41.0)
Joint pain	15.3 (10.8 to 21.1)	9.6 (6.2 to 14.7)	8.2 (5.2 to 12.7)	13.2 (10.3 to 16.8)	11.5 (9.2 to 14.3)

Population analysed: SAS included all participants who entered into the study and received at least 1 vaccination. Participants were analyzed according to the actual treatment received.

19 secondary outcomes are reported in the full results.

Adverse events

Time frame: Systematic assessment: local reactions and systemic events were assessed for up to 7 Days after each vaccination; non- systematic assessment: all-cause mortality, SAEs, AESIs were assessed up to Month 48 and other AEs (including non-SAEs) were assessed up to 28 days after each vaccination. Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
Group 1: VLA15	0 of 127 (0%)	124 of 127 (97.6%)	0 of 127
Group 2: VLA15 + Placebo	4 of 112 (3.6%)	111 of 112 (99.1%)	0 of 112
Group 3: Placebo	14 of 206 (6.8%)	145 of 206 (70.4%)	0 of 206
Received Any VLA15 Including Wrong/Missed Vaccination	14 of 419 (3.3%)	403 of 419 (96.2%)	1 of 419
All Participants	28 of 625 (4.5%)	548 of 625 (87.7%)	1 of 625

Limitations and caveats (from the sponsor): In adverse events "at risk" refers to participants who received actual treatment, regardless of the treatment group to which they were assigned at randomization.

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 15 Sep 2026.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 42680745Wagner L, Kadlecek V, Skaroupkova J, Scharnagl N, Hochreiter R, Messier M, Jaramillo JC, Larcher-Steiner J, Hegele L, Lamberth E, Murphy T, Maguire JD, Clarkin C, Derhaschnig U, Eder-Lingelbach S. A second yearly booster dose of the VLA15 Lyme borreliosis vaccine candidate in healthy individuals. Nat Commun. 2026 Aug 4;17(1):9386. doi: 10.1038/s41467-026-75871-3.
Derived from this study: PubMed 41213278Wagner L, Obersriebnig M, Hochreiter R, Kadlecek V, Larcher-Senn J, Hegele L, Maguire JD, Murphy T, Derhaschnig U, Bezay N, Jaramillo JC, Eder-Lingelbach S, Messier M. Immunogenicity and safety of an 18-month booster dose of the VLA15 Lyme borreliosis vaccine candidate after primary immunisation in children, adolescents, and adults in the USA: a randomised, observer-blind, placebo-controlled, phase 2 trial. Lancet Infect Dis. 2026 Mar;26(3):314-328. doi: 10.1016/S1473-3099(25)00541-9. Epub 2025 Nov 7.
Derived from this study: PubMed 40294611Wagner L, Obersriebnig M, Kadlecek V, Hochreiter R, Ghadge SK, Larcher-Senn J, Hegele L, Maguire JD, Derhaschnig U, Jaramillo JC, Eder-Lingelbach S, Bezay N. Immunogenicity and safety of different immunisation schedules of the VLA15 Lyme borreliosis vaccine candidate in adults, adolescents, and children: a randomised, observer-blind, placebo-controlled, phase 2 trial. Lancet Infect Dis. 2025 Sep;25(9):986-999. doi: 10.1016/S1473-3099(25)00092-1. Epub 2025 Apr 25.
To obtain contact information for a study center near you, click here.Link provided by the sponsor.
Individual participant dataSharing planned: Yes. Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Pfizer CT.gov Call Center study director

Pfizer

19 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing VLA15 in people with Lyme Borreliosis, run by Pfizer at 19 sites in United States.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 10 inclusion and 15 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 15 Sep 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 19 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 7 Jun 2023). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Percentage of Participants With Solicited Local and Solicited Systemic Adverse Events (AEs) Within 7 Days After Vaccination 1 (time frame: From Day 1 to Day 7 after vaccination 1 at Month 0). The study lists 5 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04801420, which also lists 3 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 15 Sep 2026.