A Phase 2 Clinical Trial of VLA1553 in Healthy Children Aged 1 to 11 Years

A Randomized, Observer-blinded, Dose Response Phase 2 Trial to Assess the Safety and Immunogenicity of Two Different Dose Levels of a Live-attenuated Chikungunya Virus Vaccine (VLA1553) in Healthy Children Aged 1 to 11 Years

This is a multicenter, prospective, randomized, observer-blinded, three arm, phase 2 clinical trial evaluating the full dose formulation of VLA1553, half dose formulation of VLA1553 and control.

At least 300 male and female healthy children aged 1 to 11 years will be enrolled and the overall distribution of participants will be 2:2:1 to the two VLA1553 dose groups (n=120 each) or control (n=60).

Study Overview

• Status: Completed
• Conditions: Chikungunya Virus Infection
• Intervention / Treatment: Biological: VLA1553 full dose; Biological: VLA1553 half dose; Biological: Control

Detailed Description

This is a multicenter, prospective, randomized, observer-blinded, three arm, phase 2 clinical trial evaluating the full dose formulation of VLA1553, half dose formulation of VLA1553 and control (Nimenrix, a tetravalent meningococcal vaccine - Men ACWY).

At least 300 male and female healthy children aged 1 to 11 years will be enrolled and the overall distribution of participants will be 2:2:1 to the two VLA1553 dose groups (n=120 each) or control (Nimenrix) (n=60).

As a safety precaution measure, the first 30 sentinel participants will be enrolled into the trial in an open-label fashion according to an age step down scheme.

After sentinel analysis, participants will be enrolled in a blinded, randomized manner into three Trial Arms. Within each treatment arm participants will be stratified into three age strata:

Stratum A: 7 to 11 years -children from their 7th birthday until the day before their 12th birthday.

Stratum B: 3 to 6 years - children from their 3rd birthday until the day before their 7th birthday.

Stratum C: 1 to 2 years - children from their 1st birthday until the day before their 3rd birthday.

Age strata for the VLA1553 treatment arms are targeted to be equal in size, i.e., approximately 40 per age stratum.

• Study Type: Interventional
• Enrollment (Actual): 304
• Phase: Phase 2

Contacts and Locations

Study Locations

• Dominican Republic
  • Santo Domingo, Dominican Republic, 10306
    • Instituto Dermatologico y Cirugia de la Piel "Dr Huberto Bogaert Diaz" IDCP
  • Gazcue
    • Santo Domingo, Gazcue, Dominican Republic
      • Fundacion Dominicana de Perinatologia Fundacion Probebe
• Honduras
  • Tegucigalpa, Honduras
    • Inversiones en Investigacion Medica INVERIME

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Male or female healthy children aged 7 to 11 years for Stratum A, 3 to 6 years for Stratum B and 1 to 2 years for Stratum C at the time of vaccination;
2. Written informed consent by the participant's parent(s)/Legally Acceptable Representative(s) ((LAR(s)), according to local requirements, and written informed assent of the participant, if applicable;
3. Participant was seropositive for previous CHIKV exposure (i.e., IgM+/IgG+ or IgM-/IgG+) or seronegative (i.e., IgM-/IgG-); or participants with any borderline IgM or IgG element (IgM borderline/IgG-, IgM-/IgG borderline, or IgM borderline/IgG borderline were mapped to seronegative group; participants with enzyme-linked immunosorbent assay (ELISA) result IgM borderline/IgG+ were mapped to seropositive group);

Exclusion Criteria:

1. Participant was IgM+/IgG- does not qualify for participation in this trial.
2. Participant was taking medication or other treatment for unresolved symptoms attributed to a previous CHIKV infection; or had participated in a clinical trial involving an investigational CHIKV vaccine;
3. Participant had an acute or recent infection (and was not symptom-free in the week prior to the Screening Visit (Visit 0))
4. Participant had received another live virus vaccine within 28 days or inactivated vaccine (includes messenger ribonucleic acid [mRNA] vaccines) within 14 days prior to vaccination in this trial or planned to receive a live virus vaccine within 28 days or inactivated vaccine within 14 days after vaccination;
5. Participant had abnormal findings in any required trial investigations (including medical history, physical examination, and clinical laboratory) considered clinically relevant by the Investigator which posed a risk for participation in the trial based on his/her judgment;
6. Participant had an ongoing medical history of or currently had acute or progressive, unstable or uncontrolled clinical conditions (e.g., cardiovascular, respiratory, neurologic, psychiatric, or rheumatologic conditions) that posed a risk for participation in the trial, based on Investigator's clinical judgment. Examples included individuals with poorly controlled or unstable disease, ongoing suspected or active inflammation, or poor compliance with pharmacologic treatment, or presence of high-risk comorbidities (e.g., significant cardiopulmonary disease);
7. Participant had a history of immune-mediated or clinically relevant arthritis/arthralgia;
8. Participant had a known or suspected defect of the immune system that could be expected to influence the immune response to the vaccine, such as Participants with congenital or acquired immunodeficiency, including infection with HIV, status post organ transplantation or immuno- suppressive therapy within 4 weeks prior to Visit 1. Immunosuppressive therapy was defined as administration of chronic (longer than 14 days) prednisone or equivalent ≥0.05 mg/kg/day within 4 weeks prior to trial entry, radiation therapy or immunosuppressive cytotoxic drugs/ monoclonal antibodies in the previous 3 years; topical and inhaled steroids were allowed.
9. Participant had a history of any vaccine-related contraindicating event (e.g., anaphylaxis, allergy to components of the vaccine or the control vaccine, other known contraindications including febrile convulsions);
10. Participant presented with clinical conditions representing severe bleeding disorders and medications interfering with blood clotting;
11. Participant received blood-derived products (e.g. plasma) within 180 days prior to vaccination in this trial;
12. Participant had participated in another clinical trial involving an investigational medicinal product (IMP) or device within 30 days prior to vaccination or was scheduled to participate in another clinical trial involving an IMP, or device during the course of this trial;
13. Participant had any condition that, in the opinion of the Investigator, could compromise the participant's well-being, might interfere with evaluation of trial endpoints, or would limit the participant's ability to complete the trial;
14. Participant/ Participant's parent(s)/LAR(s) was/were a member of the team conducting the trial or in a dependent relationship with one of the trial team members. Dependent relationships included close relatives (i.e., children, partner/spouse, siblings, parent(s)/LAR[s]) as well as employees of the Investigator or site personnel conducting the trial.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: VLA1553 full dose	Biological: VLA1553 full dose; Single intramuscular vaccination on Day 1 with VLA1553 full dose, a lyophilized live-attenuated Chikungunya vaccine candidate
Experimental: VLA1553 half dose	Biological: VLA1553 half dose; Single intramuscular vaccination on Day 1 with VLA1553 half dose, a lyophilized live-attenuated Chikungunya vaccine candidate
Active Comparator: Control; Single intramuscular vaccination on Day 1 with Nimenrix (Men ACWY vaccine), a conjugate vaccine indicated for the active immunization	Biological: Control; Nimenrix

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants With Solicited Injection Site Reactions	Frequency and severity of solicited injection site and solicited systemic reactions within 14 days post-vaccination.	within 14 days post-vaccination
Severity of Solicited Injection Site Reactions		within 14 days post-vaccination
Number of Participants With Solicited Systemic Reactions		within 14 days post-vaccination
Severity of Solicited Systemic Reactions		within 14 days post-vaccination

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Number of Participants With Any Adverse Event (AE)		within 28 days post-vaccination
Severity of Any Adverse Event (AE)	In the Outcome measure "Severity of any AE", subjects may be represented in more than one AE category. Therefore, the total number of subjects with any AE may be lower than the sum of the numbers of subjects in the individual AE categories (solicited / unsolicited AE).	within 28 days post-vaccination
Number of Participants With of Unsolicited AE		until Month 6 (Day 180) and Month 12 (Day 365) post-vaccination
Severity of Unsolicited AE		until Month 6 (Day 180) and Month 12 (Day 365) post-vaccination
Number of Participants With Any Serious Adverse Event (SAE)		until Month 6 (Day 180) and Month 12 (Day 365) post-vaccination
Number of Participants With Any Early Onset Adverse Event of Special Interest (AESI)	Early onset AESI were defined as: Fever (≥ 38.0 °c / 100.4 °f,) AND; symptoms suggesting acute (poly)arthralgia/arthritis, myalgia, neurological symptoms (e.g., for meningoencephalitis, acute encephalitis, headache, seizures), back pain, lymphadenopathy, cardiac or ocular symptoms (e.g., for uveitis and retinitis); OR one or more of the following signs and symptoms: macular to maculopapular rash (sometimes with cutaneous pruritus [foot plant]), pigmentary changes, bullous rash/ skin blistering, purpura, ecchymosis and; Onset of symptoms 2 to 21 days after vaccination AND; Duration of event ≥ 3 days.	2 to 21 days post-vaccination
Severity of Any Early Onset Adverse Event of Special Interest (AESI)		2 to 21 days post-vaccination
Number of Participants With Any Late Onset Adverse Event of Special Interest (AESI)		Starting 22 days post-vaccination until end of trial, 12 months post-vaccination
Severity of Any Late Onset Adverse Event of Special Interest (AESI)		Starting 22 days post-vaccination until end of trial, 12 months post-vaccination
Assessment of Viremia on Days 1, 4, 8 and 15	Number of participants with viremic results, including quantifiable results and results below LLOQ, by visit and by pooled trial arm. Day 29 was only tested, if Day 15 was tested positive. Viremia is measured in genome copy equivalents per milliliter (GCE/mL). All quantifiable results and results below LLOQ (< 3214.4 GCE/mL), but above the LOD, are considered "viremic". A result of "not detected" or below LOD (<1071,4 GCE/mL) is included as "non-viremic".	on Days 1, 4, 8 and 15 and beyond as applicable
Immune Response in Baseline Seronegative Participants as Measured by CHIKV-specific Neutralizing Antibody Titers	Immune Response provided by Geometric Mean Titers (GMTs) in Baseline Seronegative Participants pooled by Trial Arm up to 12 months post vaccination.	on Day 1, Day 15, Day 29, Day 85, Day 180 and Month 12 post-vaccination
Immune Response as Measured by CHIKV-specific Neutralizing Antibody Titers by Age Group and Trial Arm.	Immune Response provided by Geometric Mean Titers (GMTs) by Visit, by Age Group and Trial Arm up to 12 months post vaccination.	on Day 1, Day 15, Day 29, Day 85, Day 180 and Month 12 post-vaccination
Immune Response Measured by CHIKV-specific Neutralizing Antibody Titers Pooled by Dose	Immune Response provided by Geometric Mean Titers (GMTs) by Visit, pooled by Trial Arm up to 12 months post vaccination.	on Day 1, Day 15, Day 29, Day 85, Day 180 and Month 12 post-vaccination
Percentage of Participants Seronegative at Baseline With Seroconversion as Compared to Baseline	Percentage of participants seronegative at baseline with Seroconversion (defined as >4-fold titer change compared to baseline) by Visit Pooled by Trial Arm	at Day 15, Day 29, Day 85, Day 180 and Month 12
Percentage of Participants Seropositive at Baseline With Seroconversion as Compared to Baseline	Percentage of participants seropositive at baseline with Seroconversion (defined as >4-fold titer change compared to baseline) by Visit Pooled by Trial Arm.	at Day 15, Day 29, Day 85, Day 180 and Month 12
Percentage of Participants With Seroconversion as Compared to Baseline Stratified by Age Stratum	Percentage of participants with Seroconversion (defined as >4-fold titer change compared to baseline) by Visit by Age Group and Trial Arm.	at Day 15, Day 29, Day 85, Day 180 and Month 12
Percentage of Participants With Seroconversion as Compared to Baseline by Dose	Percentage of participants with Seroconversion (defined as >4-fold titer change compared to baseline) by Visit Pooled by Trial Arm	at Day 15, Day 29, Day 85, Day 180 and Month 12
Percentage of Participants Seronegative at Baseline With a Seroresponse (Defined as PRNT50 ≥150 for Baseline Negative Participants) by Dose	Percentage of Participants with Seroresponse for CHIKV-Specific Neutralizing Antibody Titers (defined as PRNT50 ≥150) by Visit Pooled by Trial Arm.	on Day 15, Day 29, Day 85, Day 180 and Month 12 post-vaccination
Percentage of Participants With a Seroresponse Stratified by Age Stratum	Percentage of Participants with Seroresponse for CHIKV-Specific Neutralizing Antibody Titers (defined as PRNT50 ≥150) by Visit by Age Group and Trial Arm.	on Day 15, Day 29, Day 85, Day 180 and Month 12 post-vaccination
Percentage of Participants With a Seroresponse Stratified by Dose	Percentage of Participants with Seroresponse for CHIKV-Specific Neutralizing Antibody Titers (defined as PRNT50 ≥150) by Visit Pooled by Trial Arm.	on Day 15, Day 29, Day 85, Day 180 and Month 12 post-vaccination
Fold Change of CHIKV-specific Neutralizing Antibody Titers as Compared to Baseline in Participants Seronegative at Baseline	Fold Change for CHIKV-Specific Neutralizing Antibody Titers in seronegative Participants by Visit Pooled by Trial Arm.	at Days 15, 29, 85, 180 and at Month 12 post-vaccination
Fold Change of CHIKV-specific Neutralizing Antibody Titers as Compared to Baseline in Seropositive Participants	Fold Change for CHIKV-Specific Neutralizing Antibody Titers in seropositive Participants by Visit Pooled by Trial Arm.	at Days 15, 29, 85, 180 and at Month 12 post-vaccination
Fold Change of CHIKV-specific Neutralizing Antibody Titers as Compared to Baseline Stratified by Age Stratum	Fold Change for CHIKV-Specific Neutralizing Antibody Titers by Visit by Age Group and Trial Arm.	at Days 15, 29, 85, 180 and at Month 12 post-vaccination
Fold Change of CHIKV-specific Neutralizing Antibody Titers as Compared to Baseline Stratified by Dose	Fold Change for CHIKV-Specific Neutralizing Antibody Titers by Visit Pooled by Trial Arm.	at Days 15, 29, 85, 180 and at Month 12 post-vaccination
Percentage of Participants Seronegative at Baseline Reaching an at Least 4-fold, 8-fold, 16-fold or 64-fold Change in CHIKV-specific Neutralizing Antibody Titers Compared to Baseline	Percentage of Participants Reaching a 4-/8-/16-/64-Fold Change in Titers by Visit Pooled by Trial Arm.	at Day 15, Day 29, Day 85, Day 180 and Month 12
Percentage of Participants Reaching an at Least 4-fold, 8-fold, 16-fold or 64-fold Change in CHIKV-specific Neutralizing Antibody Titers Compared to Baseline Stratified by Age Stratum	Percentage of Participants Reaching a 4-/8-/16-/64-Fold Change in Titers by Visit by Age Group and Trial Arm.	at Day 15, Day 29, Day 85, Day 180 and Month 12
Percentage of Participants Reaching an at Least 4-fold, 8-fold, 16-fold or 64-fold Change in CHIKV-specific Neutralizing Antibody Titers Compared to Baseline by Dose	Percentage of Participants Reaching a 4-/8-/16-/64-Fold Change in Titers by Visit Pooled by Trial Arm.	at Day 15, Day 29, Day 85, Day 180 and Month 12

Collaborators and Investigators

• Sponsor: Valneva Austria GmbH
• Investigators: Study Chair: Valneva Clinical Development, Valneva Austria GmbH

Publications and helpful links

General Publications

• Weisova P, Scheiblauer S, Ecker J, Schneider M, Hochreiter R, Bitzer A, Kosulin K, Schoengrundner P, Fuchs U, Rodeles L, Mazara S, Donastorg Y, Rivera S, Wressnigg N, Dubischar K, Buerger V, Eder-Lingelbach S, Jaramillo JC. Live-attenuated chikungunya vaccine in children: a randomized phase 2 trial. Nat Med. 2026 Feb;32(2):561-571. doi: 10.1038/s41591-025-04197-2. Epub 2026 Feb 6.

Study record dates

Study Major Dates

• Study Start (Actual): December 18, 2023
• Primary Completion (Actual): July 31, 2024
• Study Completion (Actual): July 2, 2025

Study Registration Dates

• First Submitted: October 24, 2023
• First Submitted That Met QC Criteria: October 24, 2023
• First Posted (Actual): October 30, 2023

Study Record Updates

• Last Update Posted (Actual): August 13, 2026
• Last Update Submitted That Met QC Criteria: July 21, 2026
• Last Verified: August 1, 2025

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: VLA1553-221

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: 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.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No