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).

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.

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.

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.