Evaluation of IXCHIQ® Vaccine Immunogenicity

• IXCHIQ vaccine (Biological): Live-attenuated monovalent vaccine against Chikungunya virus - IXCHIQ

Primary outcomes

• Celular immunogenicity [3 years]: Number and percentage of the various vaccine-induced mononuclear and polymorphonuclear populations, as assessed by flow cytometry, comparing age groups.

Secondary outcomes

• Safety evaluation [60 days]: To evaluate the incidence of adverse events, particularly adverse events of special interest (Chikungunya-like adverse events \[CLARs\], carditis, encephalitis, and grade 3 or higher adverse events), up to 60 days after vaccination.
• Neutralizing antibodies duration [3 years]: Titer of antibodies capable of neutralizing a Brazilian Chikungunya strain and the vaccine strain in a plaque neutralization assay.
• Immunological profile evaluation [3 years]: Titer of antibodies capable of neutralizing a Brazilian Chikungunya strain and the vaccine strain in a plaque neutralization assay.
• Immunological crossover [3 years]: Correlation matrix-in the form of correlograms or heatmaps-of the humoral and cellular response.

Sex: All, ages: 12 Years to 59 Years, accepts healthy volunteers

Inclusion criteria:

* The participant or guardian understands the procedures and requirements, and is willing and able to provide informed consent for full participation in the study;
* Individuals of both sexes aged 12 to 59 years.

Exclusion Criteria:

* Participants under 12 years of age or 60 years of age or older;
* Those with any contraindication identified in Ministry of Health Technical Note No. 9/2026-CGFAM/DPNI/SVSA/MS (https://www.gov.br/saude/pt-br/centrais-de-conteudo/publicacoes/notas-tecnicas/2026/nota-tecnica-no-9-2026-cgfam-dpni-svsa-ms.pdf - Technical Note: Guidelines for monitoring the safety of the Chikungunya vaccine used during the pilot vaccination strategy in Brazil - 2026);
* Participants unavailable to attend the planned study visits;
* Participants who do not agree to sign the Informed Consent Form (ICF);
* Positive β-hCG test on the day of vaccination, for women of reproductive potential;
* Participants who are pregnant or planning to become pregnant within the 3 months following the vaccine dose;
* Participants who are breastfeeding;
* Participants with a known or suspected immune system defect that could influence the immune response to the vaccine, such as congenital or acquired immunodeficiency-including HIV infection, post-organ transplant status, or immunosuppressive therapy within 4 weeks prior to Visit 1. Immunosuppressive therapy is defined as the chronic administration of prednisone (more than 14 days) or an equivalent at a dosage of ≥2 mg/kg/day during the 4 weeks prior to study entry. Note: radiotherapy or cytotoxic immunosuppressive drugs/monoclonal antibodies within the previous 3 years; topical and inhaled steroids are permitted.
* Any clinical instability identified by the attending physician that could place the participant at risk.

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• Study Protocol and Statistical Analysis Plan (PDF, 2026-08-25)

• Mauro M Teixeira, MD, Phd, Principal investigator, Federal University of Minas Gerais