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

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).

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 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 Exclusion Criteria: * 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.