Chikungunya Virus InfectionPhase 3NCT04838444

Antibody Persistence And Long Term Safety Of A Chikungunya Virus Vaccine (VLA1553)

A Phase 3 study testing VLA1553 in people with Chikungunya Virus Infection, run by Valneva Austria GmbH at 10 sites in United States.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record

Search all trials

Trial summary

In this open-label Phase 3b, single arm trial, persistence of antibodies and long term safety will be evaluated in up to 375 participants rolled over from trial VLA1553-301 (NCT number: NCT04546724). Read more about this study

Who is it for?: Ages 18 years and olderHealthy volunteers can take part
Conditions the study is for: Chikungunya Virus Infection
What is being tested?: VLA1553
Type of treatment: Vaccines
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 363 participants
Where: 10 sitesUnited States
Study dates: 2 Apr 2021to May 2031
Phase: Phase 3
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 18 years and older
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Individual participated in the VLA1553-301 clinical trial;
Participant has an understanding of the trial and its procedures, agrees to its provisions, and voluntarily gives written informed consent prior to any trial-related procedures;
Participant had immunogenicity blood samples taken at baseline (Visit 1) and either Day 29 (Visit 3), Day 85 (Visit 4) or Day 180 (Visit 5) in Trial VLA1553-301 and was negative for neutralizing antibodies at baseline

Who cannot join

Participant presents with clinical conditions representing a contraindication to blood draws;
Participant has donated blood or use of blood products prior 30 days of immunogenicity sampling;
Participant has received an active drug with potential immunosuppressive action or investigational drug or device within a period of 30 days prior a trial visit;
Participant has a known or suspected problem with alcohol or drug abuse as determined by the Investigator;
Participant has any condition that, in the opinion of the Investigator, may compromise the participant's well-being, might interfere with evaluation of trial endpoints, or would limit the participant's ability to complete the trial;
Participant is committed to an institution (by virtue of an order issued either by the judicial or the administrative authorities);
Participant is a member of the team conducting the trial or in a dependent relationship with one of the trial team members. Dependent relationships include close relatives (i.e., children, partner/spouse, siblings, parents) as well as employees of the Investigator or site personnel conducting the trial.

Trial locations and contacts

10 sites in 1 country.

City, postcode or hospital

10 sites in 1 country

United States10 sites

Velocity Clinical Research
Austin, Texas, 78759
Accelerated Enrollment Solutions (AES)
Chicago, Illinois, 60602
Velocity Clinical Research
Grand Island, Nebraska, 68803
Velocity Clinical Research
Hallandale, Florida, 33090
Alliance for Multispecialty Research (AMR)
Knoxville, Tennessee, 37920
Alliance for Multispecialty Research (AMR)
Lexington, Kentucky, 40509
Allliance for Multispecialty Research (AMR)
Norfolk, Virginia, 23502
Velocity Clinical Research
Omaha, Nebraska, 68134
Accelerated Enrollment Solutions (AES)
Phoenix, Arizona, 85020
Velocity Clinical Research
West Jordan, Utah, 84088

Other trials in United States

About this study

Official title: An Open-Label, Single Arm Trial To Evaluate Antibody Persistence And Long Term Safety Of A Live-Attenuated Chikungunya Virus Vaccine (VLA1553) In Adults Aged 18 Years and Above

In this open-label Phase 3b, single arm trial, persistence of antibodies and long term safety will be evaluated in up to 375 participants rolled over from trial VLA1553-301 (NCT number: NCT04546724).

Read the detailed description

In this open-label Phase 3b, single arm trial, persistence of antibodies and long term safety in up to 375 participants rolled over from trial VLA1553-301 (NCT number: NCT04546724)

These participants will have annual follow-up visits at Months 12, 24, 36, 48, 60, 72, 84, 96, 108 and 120 after immunization. The primary objective of this trial will be to evaluate persistence of antibodies annually from 1 to 10 years after the single immunization with VLA1553. The secondary objective is to evaluate long-term safety 6 months to 2 years after the single immunization with VLA1553.

Conditions: Chikungunya Virus Infection
Being tested: VLA1553
Medical subject headings: Chikungunya Fever

What participants receive

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

VLA1553Biological
Trial participants previously vaccinated with VLA1553 in trial VLA1553-301 will be followed up for safety and immunogenicity.

Study groups in NCT04838444
Study group	Role	What they receive
VLA1553	Experimental	Not described Receives: Biological: VLA1553

What is being measured

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

Proportion of Participants With Seroresponse Levels Post-vaccination. (Defined as µPRNT50 ≥150)
Data for Visit 1 - Day 1 are collected from Trial VLA1553-301
Measured: Year 2

Secondary outcomes (6)

Frequency of Any Serious Adverse Event (SAE)
Measured: until Year 2
Relatedness of Any Serious Adverse Event (SAE)
Measured: until Year 2
Immune Response as Measured by CHIKV-specific Neutralizing Antibody Titers Post-vaccination
Measured: until Year 10
Proportion of Participants With Seroconversion
Measured: until Year 10
Fold Increase of CHIKV-specific Neutralizing Antibody Titers Post-vaccination as Compared to Baseline (i.e. at Start of Trial VLA1553-301)
Measured: until Year 10
Proportion of Participants Reaching an at Least 4-fold, 8-fold, 16-fold or 64-fold Increase in CHIKV-specific Neutralizing Antibody Titer Compared to Baseline
Measured: until Year 10

Timeline

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

2 Apr 2021May 2031

First posted9 Apr 2021
Study start2 Apr 2021
Primary completion3 Mar 2023
Study completionMay 2031 (estimated)

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 (1)Papers the sponsor has linked to this study.
Other trials for Chikungunya Virus InfectionStudies of the same condition, open and under way.
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 3
Primary purpose: Prevention
Allocation: Not applicable
Intervention model: Single group
Masking: None (open label)
Enrolment: 363 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04838444
Sponsor's protocol ID: VLA1553-303
Status last verified: Aug 2025
First submitted: 6 Apr 2021
Last updated: 9 Jul 2026
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: After trial completion, Valneva may provide access to individual de-identified participant data and related trial documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Trial Report (CTR)) upon request from qualified researchers, and subject to Valneva's review and approval.

Publications

McMahon R, Toepfer S, Sattler N, Schneider M, Narciso-Abraham M, Hadl S, Hochreiter R, Kosulin K, Mader R, Zoihsl O, Wressnigg N, Dubischar K, Buerger V, Eder-Lingelbach S, Jaramillo JC. Antibody persistence and safety of a live-attenuated chikungunya virus vaccine up to 2 years after single-dose administration in adults in the USA: a single-arm, multicentre, phase 3b study. Lancet Infect Dis. 2024 Dec;24(12):1383-1392. doi: 10.1016/S1473-3099(24)00357-8. Epub 2024 Aug 12.
PubMed 39146946

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?

See locations

Active, not recruitingPhase 3
A Safety and Immunogenicity Study of CHIKV VLP Vaccine in Children.
Chikungunya Virus
Not yet recruitingPhase 2
Evaluation of IXCHIQ® Vaccine Immunogenicity
Healthy Adult, Healthy Adolescents
RecruitingPhase 4
Real-world Effectiveness, Safety & Immunogenicity of Chikungunya Vaccination: Ambispective Study in Reunion & French Guiana
Chikungunya Virus Infection
Recruiting
Against Chikungunya Virus and Neonatal Infection
Chikungunya Virus Infection, Neonatal
Enrolling by invitation
Smart Analysis and Decision-Making for Emerging Infectious Diseases
Emerging Infectious Diseases, COVID-19

All Chikungunya Virus Infection trials

Study at a glance

From the registry record, last updated by the sponsor on 9 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: An Open-Label, Single Arm Trial To Evaluate Antibody Persistence And Long Term Safety Of A Live-Attenuated Chikungunya Virus Vaccine (VLA1553) In Adults Aged 18 Years and Above
ClinicalTrials.gov ID: NCT04838444
Acronym / sponsor ID: VLA1553-303
Conditions: Chikungunya Virus Infection
Phase: Phase 3
Study type: Interventional
Recruitment status: Active, not recruiting
Enrolment: 363 participants (actual)
Lead sponsor: Valneva Austria GmbHIndustry (pharma, biotech, devices)
Study start: 2 Apr 2021 (actual)
Primary completion: 3 Mar 2023 (actual)
Study completion: May 2031 (estimated)
First posted: 9 Apr 2021 (actual)
Results: Posted 9 Jul 2026

Clinical summary

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

In this open-label Phase 3b, single arm trial, persistence of antibodies and long term safety will be evaluated in up to 375 participants rolled over from trial VLA1553-301 (NCT number: NCT04546724).

Detailed description

In this open-label Phase 3b, single arm trial, persistence of antibodies and long term safety in up to 375 participants rolled over from trial VLA1553-301 (NCT number: NCT04546724)

Study design

Primary purpose: Prevention
Allocation: Not applicable
Intervention model: Single group
Masking: None (open label)
Number of arms: 1

Arm	Type	Receives
VLA1553	Experimental	Biological: VLA1553

Who may qualify

Ages: 18 years and older
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (3 listed)

Individual participated in the VLA1553-301 clinical trial;
Participant has an understanding of the trial and its procedures, agrees to its provisions, and voluntarily gives written informed consent prior to any trial-related procedures;
Participant had immunogenicity blood samples taken at baseline (Visit 1) and either Day 29 (Visit 3), Day 85 (Visit 4) or Day 180 (Visit 5) in Trial VLA1553-301 and was negative for neutralizing antibodies at baseline

Key exclusion criteria (7 listed)

Participant presents with clinical conditions representing a contraindication to blood draws;
Participant has donated blood or use of blood products prior 30 days of immunogenicity sampling;
Participant has received an active drug with potential immunosuppressive action or investigational drug or device within a period of 30 days prior a trial visit;
Participant has a known or suspected problem with alcohol or drug abuse as determined by the Investigator;
Participant has any condition that, in the opinion of the Investigator, may compromise the participant's well-being, might interfere with evaluation of trial endpoints, or would limit the participant's ability to complete the trial;

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
VLA1553Trial participants previously vaccinated with VLA1553 in trial VLA1553-301 will be followed up for safety and immunogenicity.	Biological	VLA1553

Primary outcome

Proportion of Participants With Seroresponse Levels Post-vaccination. (Defined as µPRNT50 ≥150)
Time frame: Year 2
Data for Visit 1 - Day 1 are collected from Trial VLA1553-301

6 secondary outcomes

Frequency of Any Serious Adverse Event (SAE)
Time frame: until Year 2
Relatedness of Any Serious Adverse Event (SAE)
Time frame: until Year 2
Immune Response as Measured by CHIKV-specific Neutralizing Antibody Titers Post-vaccination
Time frame: until Year 10
Proportion of Participants With Seroconversion
Time frame: until Year 10
Fold Increase of CHIKV-specific Neutralizing Antibody Titers Post-vaccination as Compared to Baseline (i.e. at Start of Trial VLA1553-301)
Time frame: until Year 10
Proportion of Participants Reaching an at Least 4-fold, 8-fold, 16-fold or 64-fold Increase in CHIKV-specific Neutralizing Antibody Titer Compared to Baseline
Time frame: until Year 10

Results and safety

Results posted to the registry on 9 Jul 2026, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
VLA1553	363	317

Primary outcome: Proportion of Participants With Seroresponse Levels Post-vaccination. (Defined as µPRNT50 ≥150)

Time frame: Year 2. Number (95% Confidence Interval). Unit: percentage of participants with SRR

Measure	VLA1553: 18 - 64 Years n = 290	VLA1553: >=65 Years n = 49
Visit 1 - Day 1	0 (0.0 to 0.0)	0 (0.0 to 0.0)
Visit 1 - Year 1	99.4 (96.5 to 100.0)	100 (87.2 to 100.0)
Visit 2 - Year 2	97 (93.9 to 98.8)	97.6 (87.4 to 99.9)

Population analysed: The Per Protocol Population (PPP) is a subset of the WSP and contains * All participants who were CHIKV-seronegative at baseline (defined as μPRNT50 titer ≤40). * Have at least one or more evaluable post-baseline titer measurements at either Day 29, Day 85 or Day 180 (within SAP visit windows for trial VLA1553-301). * In addition, the participants must have no major PDs at the start of VLA1553-303 trial being analyzed that could impact immune response.

6 secondary outcomes are reported in the full results.

Adverse events

Time frame: Long-term safety (i.e. Serious Adverse Events [SAEs]) was collected 6 months to 2 years after the single immunization with VLA1553.. Other adverse events reported at 0% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
VLA1553: 18 - 64 Years	6 of 310 (1.9%)	0 of 0	1 of 310
VLA1553: >=65 Years	2 of 53 (3.8%)	0 of 0	0 of 53

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 9 Jul 2026.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 39146946McMahon R, Toepfer S, Sattler N, Schneider M, Narciso-Abraham M, Hadl S, Hochreiter R, Kosulin K, Mader R, Zoihsl O, Wressnigg N, Dubischar K, Buerger V, Eder-Lingelbach S, Jaramillo JC. Antibody persistence and safety of a live-attenuated chikungunya virus vaccine up to 2 years after single-dose administration in adults in the USA: a single-arm, multicentre, phase 3b study. Lancet Infect Dis. 2024 Dec;24(12):1383-1392. doi: 10.1016/S1473-3099(24)00357-8. Epub 2024 Aug 12.
Individual participant dataSharing planned: Yes. After trial completion, Valneva may provide access to individual de-identified participant data and related trial documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Trial Report (CTR)) upon request from qualified researchers, and subject to Valneva's review and approval.

Related trials for Chikungunya Virus Infection

Active, not recruitingPhase 3
A Safety and Immunogenicity Study of CHIKV VLP Vaccine in Children.
Chikungunya Virus
Not yet recruitingPhase 2
Evaluation of IXCHIQ® Vaccine Immunogenicity
Healthy Adult, Healthy Adolescents
RecruitingPhase 4
Real-world Effectiveness, Safety & Immunogenicity of Chikungunya Vaccination: Ambispective Study in Reunion & French Guiana
Chikungunya Virus Infection
Recruiting
Against Chikungunya Virus and Neonatal Infection
Chikungunya Virus Infection, Neonatal
Enrolling by invitation
Smart Analysis and Decision-Making for Emerging Infectious Diseases
Emerging Infectious Diseases, COVID-19

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.

Valneva Clinical Development study chair

Valneva Austria GmbH

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

Questions about this trial

What is this clinical trial studying?

A Phase 3 study testing VLA1553 in people with Chikungunya Virus Infection, run by Valneva Austria GmbH at 10 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 3 inclusion and 7 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: under way, not looking for participants, as of the sponsor's last update on 9 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 10 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. 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 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.

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 9 Jul 2026). 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?

Proportion of Participants With Seroresponse Levels Post-vaccination. (Defined as µPRNT50 ≥150) (time frame: Year 2). 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 NCT04838444, which also lists 1 linked publication.

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 9 Jul 2026.