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VLA1553

Phase 3

Chikungunya Virus Infection | Monoclonal antibody | Other |Valneva SE|Last Updated: Dec 24, 2025

Success Probability
Approval Probability 71%
TA Base Rate26%
Adjusted LOA41%
ML RiskLOW_RISK
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Market & Valuation
rNPV $3.2B
Market Size $9.4B
Revenue Basis $1.6B
Competitors 6
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Trial Design
RandomizedDouble-BlindPLACEBO_CONTROLLEDDMCBiomarker
Total Trials2
Total Enrollment4,491
FDA Designations
No designations recorded
Clinical Trials (2)
NCT IDTitlePhaseStatusEnrollmentVelocityDesignStartCompletionLast UpdatedSitesCountries
NCT04838444Antibody Persistence And Long Term Safety Of A Chikungunya Virus Vaccine (VLA1553)PHASE3 ACTIVE NOT_RECRUITING 363Apr 2, 2021May 1, 2031Dec 24, 202510 United States
NCT04546724Pivotal Study to Evaluate Safety and Immunogenicity of a Live-Attenuated Chikungunya Virus Vaccine Candidate in AdultsPHASE3 COMPLETED 4,128Sep 17, 2020Oct 15, 2021Jun 28, 202344 United States
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Study Endpoints
Primary Endpoints
Proportion of participants with seroresponse levels post-vaccination. (defined as µPRNT50 ≥150)
until Year 10
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.

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
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 — 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)
LOWMay 26, 2026NCT04838444primaryCompletionDate: changed
LOWMay 24, 2026NCT04838444studyFirstPostDate: changed