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VLA1553

Phase 3

Chikungunya Virus Infection | Monoclonal antibody | Infectious Disease |Valneva SE|Last Updated: Jul 9, 2026

Success Probability

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Trial Design

RandomizedDouble-BlindPLACEBO_CONTROLLEDDMC
Total Trials2
Total Enrollment4,491

FDA Designations

No designations recorded

Clinical trial landscape

VLA1553 · 3 trials · 2 indications

Phase 3 2Phase 1 1
NCT04838444Antibody Persistence And Long Term Safety Of A Chikungunya Virus Vaccine (VLA1553)Chikungunya Virus Infection
ACTIVE NOT_RECRUITING363 Analytics
NCT04546724Pivotal Study to Evaluate Safety and Immunogenicity of a Live-Attenuated Chikungunya Virus Vaccine Candidate in AdultsChikungunya Virus Infection
COMPLETED4,128 Analytics
PHASE3ACTIVE NOT_RECRUITING
Antibody Persistence And Long Term Safety Of A Chikungunya Virus Vaccine (VLA1553)
Chikungunya Virus InfectionUnlock trial analytics
PHASE3COMPLETED
Pivotal Study to Evaluate Safety and Immunogenicity of a Live-Attenuated Chikungunya Virus Vaccine Candidate in Adults
Chikungunya Virus InfectionUnlock trial analytics

Study Endpoints

Primary Endpoints

Proportion of Participants With Seroresponse Levels Post-vaccination. (Defined as µPRNT50 ≥150)
Year 2

Data for Visit 1 - Day 1 are collected from Trial VLA1553-301

Number of Participants With a Seroprotective CHIKV Antibody Level for Baseline Negative Subjects 28 Days Post-vaccination
on Day 29 after single vaccination

Seroprotection rate, based on a surrogate of protection agreed with FDA Assay used for analysis was based on µPRNT (Micro Plaque Reduction Neutralization Test). Participants at pre-selected sites were included, if they had available Day 1 and Day 29 samples and without major protocol deviations that could impact the immune response.

Frequency of solicited injection site reactions
up to Day 14 after single vaccination

Any measurable injection site reaction will be measured by size and includes injection site pain, tenderness, erythema/redness, induration and swelling.

Severity of solicited injection site reactions
up to Day 14 after single vaccination

Any measurable injection site reaction will be measured by size and includes injection site pain, tenderness, erythema/redness, induration and swelling. They will be rated according to the Severity Grading Scale of Injection Site Reactions (FDA Guidance on Toxicity Grading Scales for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials (FDA 2007)

Frequency of solicited systemic reactions
up to Day 14 after single vaccination

Systemic reactions including fever, nausea/vomiting, headache, fatigue, myalgia (muscle pain), arthralgia (joint pain) and rash will be reported in a standardized manner

Severity of solicited systemic reactions
up to Day 14 after single vaccination

Systemic reactions including fever, nausea/vomiting, headache, fatigue, myalgia (muscle pain), arthralgia (joint pain) and rash will be reported in a standardized manner. They will be rated according to the FDA Guidance on Toxicity Grading Scales

Secondary Endpoints

Frequency of Any Serious Adverse Event (SAE)
until Year 2
Relatedness of Any Serious Adverse Event (SAE)
until Year 2
Immune Response as Measured by CHIKV-specific Neutralizing Antibody Titers Post-vaccination
until Year 10
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Study Design & Arms

AllocationNA
MaskingNONE
ModelSINGLE_GROUP
PurposePREVENTION

Treatment Arms

ArmTypeDescription
VLA1553EXPERIMENTAL -
PlaceboPLACEBO_COMPARATORSingle intramuscular vaccination on Day 1 with Phosphate-Buffered Saline (PBS) as placebo
VLA1553 low doseACTIVE_COMPARATORVLA1553 with 3.2x10\^3 TCID50/ 100 µL (microliter). Re-vaccination at Month 12 with VLA1553 with 3.2x10\^5 TCID50/ 1 mL (milliliter)
VLA1553 medium doseACTIVE_COMPARATORVLA1553 with 3.2x10\^4 TCID50/ 1 mL Re-vaccination at Month 12 with VLA1553 with 3.2x10\^5 TCID50/ 1 mL
VLA1553 high doseACTIVE_COMPARATORVLA1553 with 3.2x10\^5 TCID50/ 1 mL Re-vaccination at Month 6 or Month 12 with VLA1553 with 3.2x10\^5 TCID50/ 1 mL

Interventions

NameTypeDescription
VLA1553BIOLOGICALTrial participants previously vaccinated with VLA1553 in trial VLA1553-301 will be followed up for safety and immunogenicity.
PlaceboBIOLOGICALSingle intramuscular vaccination on Day 1 with Phosphate-Buffered Saline (PBS) as placebo
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Eligibility Criteria

Age Range18 Years to N/A
SexALL
Healthy VolunteersYes
Study Sites10

Inclusion Criteria: * 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...

Countries:United States
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Recent Changes (Last 90 Days)

LOWJul 9, 2026NCT04838444primaryCompletionDate: changed
LOWJul 9, 2026NCT04838444primaryCompletionDate: changed
LOWMay 26, 2026NCT04838444primaryCompletionDate: changed
LOWMay 24, 2026NCT04838444studyFirstPostDate: changed

Frequently asked questions about VLA1553

What is VLA1553 used for?

VLA1553 is an investigational vaccine candidate for the prevention of chikungunya and chikungunya virus infection. It is being developed as a live-attenuated vaccine to generate an immune response against the chikungunya virus. The vaccine is currently in clinical development and is not yet approved by regulatory authorities.

Who makes VLA1553?

VLA1553 is being developed by Valneva SE, a biopharmaceutical company traded on the NASDAQ under the ticker symbol VALN. Valneva is conducting clinical trials to evaluate the safety and immunogenicity of the vaccine candidate in healthy adult volunteers.

What phase is VLA1553 in?

VLA1553 is in Phase 3 clinical development. The pivotal Phase 3 study (NCT04546724) has been completed, and a long-term follow-up study (NCT04838444) is active but not recruiting. An earlier Phase 1 study (NCT03382964) was also completed. The vaccine remains investigational and has not received FDA approval.

What clinical trials is VLA1553 in?

VLA1553 has been studied in three clinical trials. NCT03382964 was a Phase 1 study in 120 healthy volunteers in the United States. NCT04546724 was a pivotal Phase 3 study in 4,128 adults. NCT04838444 is an active Phase 3 study evaluating antibody persistence and long-term safety in 363 participants.

How does VLA1553 work?

VLA1553 is a live-attenuated vaccine designed to induce an immune response against the chikungunya virus. By presenting weakened virus components to the immune system, it aims to stimulate the production of antibodies that can neutralize the virus and provide protection against chikungunya infection.

Is VLA1553 the same as a chikungunya vaccine?

VLA1553 is a chikungunya virus vaccine candidate. It is specifically designed to prevent chikungunya and chikungunya virus infection. The vaccine is being developed by Valneva SE and is currently in Phase 3 clinical trials, with studies completed or ongoing in the United States.