Prospective Safety Cohort Study After VLA1553 Vaccination in Municipalities Selected for Participation in the VLA1553 Pilot Vaccination Strategy in Brazil

Prospective Safety Cohort Study VLA1553-406

This is an observational study with primary data collection, which will combine a prospective safety cohort study and an SCRI study.

Study Overview

• Status: Enrolling by invitation
• Conditions: Chikungunya Virus Infection
• Intervention / Treatment: Biological: Live-attenuated CHIKV vaccine VLA1553

Detailed Description

This prospective safety cohort study will be conducted in selected Brazilian municipalities participating in a pilot vaccination strategy. A total of 5,000 participants will be recruited. The primary objective is to estimate the incidence rates of a predefined set of AEs which constitute safety concerns. The secondary objectives are to measure the relative risk associated with VLA1553 administration for a predefined set of AEs which constitute safety concerns, and to assess the frequency of occurrence of any collected AE which are medically attended or meet the criteria of seriousness This study also aims to investigate VLA1553's safety in underrepresented populations by collecting all AEs, not just AEs which constitute safety concerns.

• Study Type: Observational
• Enrollment (Estimated): 5000

Contacts and Locations

Study Locations

• Brazil
  • Ceará
    • Fortaleza, Ceará, Brazil, 60430-160
      • Universidade Federal do Ceara
  • Minas Gerais
    • Belo Horizonte, Minas Gerais, Brazil, 31270-901
      • Universidade Federal de Minas Gerais, CT Terapias Avançadas e Inovadoras
  • Sergipe
    • Laranjeiras, Sergipe, Brazil, 49060-025
      • Centro de Pesquisas Clínicas Universidade Federal Sergipe, Hospital e Maternidade São João de Deus
  • São Paulo
    • São Pedro, São Paulo, Brazil, 15090-000
      • Fundação Faculdade Regional de Medicina de São José do Rio Preto

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

This study will collect data from approximately 5,000 individuals who received VLA1553, as per label, as part of the pilot vaccination strategy in selected municipalities in Brazil.

Description

Inclusion Criteria:

1. Male or female participants who received a single dose of VLA1553 at a vaccination unit while participating in the pilot vaccination strategy.
2. Individuals that are target for the pilot vaccination strategy at the time of vaccination.
3. Individuals understanding and being able to comply with all scheduled follow-up calls/contacts and study procedures.
4. Have given informed consent/assent prior to entering the study.

Exclusion Criteria:

1. Individuals who have received investigational products within the 30 days prior to VLA1553 vaccination, or individuals who have received VLA1553/IXCHIQ previously or any authorized or approved CHIKV vaccine.
2. Individuals residing outside of the study municipalities or are not expected to remain in the study municipalities for the next 24 weeks after vaccination.
3. Pregnant women: women exposed to VLA1553 anytime during their pregnancy or within 30 days preceding their last menstrual period will be invited to participate in a separate pregnancy surveillance study (study identifier VLA1553-403).

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
To estimate the incidence rates of a predefined set of AEs which constitute safety concerns according to the VLA1553 Risk Management Plan following the administration of the live-attenuated VLA1553 vaccine	For each safety concern, the risk windows after VLA1553 administration are defined as: 30 days for Chikungunya-like adverse reactions;; 60 days for cardiac events, choosing a more conservative window than the 42 days suggested by the Brighton Collaboration recommendations on myocarditis;; 60 days for arthritis to account for late-onset or potentially immune-mediated cases	From enrollment until Day 60

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
To measure the relative risk associated with VLA1553 administration for a predefined set of AEs which constitute safety concerns as per the VLA1553 Risk Management Plan for those AEs that have a defined risk window following vaccination.		From enrollment until Day 120
To assess the frequency of occurrence of predefined AEs which are medically attended or meet the criteria of seriousness.	Frequency of occurrence of predefined chronic chikungunya-like adverse reactions;; frequency of predefined SAEs;; frequency of occurrence of arthralgia;; frequency of occurrence of prolonged arthralgia;; frequency of predefined CHIKV infection symptoms;; frequency of occurrence of predefined chronic CHIKV infection symptoms	From enrollment until Month 6

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
To assess the frequency of occurrence of AEs (not exclusively those of safety concern) following VLA1553 vaccination when co-administered or concomitantly administered with other vaccines.		From enrollment until Month 6
To assess the frequency of occurrence of AEs (not exclusively those of safety concern) in populations underrepresented or excluded in clinical trials with VLA1553.	Individuals aged ≥ 65 years old (including those with chronic medical conditions);; individuals with acute or progressive, unstable, or uncontrolled clinical conditions;; individuals with autoimmune or inflammatory disorders (including with impaired or dysregulated immune responses);	From enrollment until Month 6

Collaborators and Investigators

• Sponsor: Valneva Austria GmbH
• Collaborators: Coalition for Epidemic Preparedness Innovations; Fundação Butantan

Study record dates

Study Major Dates

• Study Start (Actual): February 2, 2026
• Primary Completion (Estimated): October 31, 2026
• Study Completion (Estimated): February 28, 2027

Study Registration Dates

• First Submitted: November 19, 2025
• First Submitted That Met QC Criteria: November 19, 2025
• First Posted (Actual): November 28, 2025

Study Record Updates

• Last Update Posted (Actual): February 11, 2026
• Last Update Submitted That Met QC Criteria: February 9, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vector Borne Diseases; Mosquito-Borne Diseases; Infections; RNA Virus Infections; Virus Diseases; Arbovirus Infections; Alphavirus Infections; Togaviridae Infections; Chikungunya Fever
• Other Study ID Numbers: VLA1553-406

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No