IXCHIQ Chikungunya Vaccine Trial Shows Sustained Immune Response in Adolescents

Valneva SE, who developed the world’s first FDA-approved chikungunya vaccine, has now unveiled promising Phase III data for its single-shot chikungunya vaccine, IXCHIQ, in adolescents aged 12 to 17. Following the announcement, Valneva’s stock rose by 1.4%.

IXCHIQ is the only licensed chikungunya vaccine in the US for adults aged 18 and older at increased risk of exposure to the virus.

The findings reveal a remarkable 98.3% seroresponse rate — indicating the proportion of participants achieving antibody levels above a predefined protective threshold — sustained one year after vaccination.

Chikungunya, a mosquito-borne viral disease, causes severe joint pain, fever and rash, with symptoms that can linger for months or even years.

The VLA1553-321 trial, conducted in Brazil, was the first to assess the vaccine in an endemic region.

The study included 754 adolescents, comparing immune responses and safety profiles between vaccine and placebo groups. Participants received a single intramuscular dose of the vaccine, and results consistently exceeded the seroresponse threshold defined by the FDA as a marker of protection.

One year post-vaccination, antibody levels remained strong, with geometric mean titers well above the required protective threshold.

These sustained responses build on earlier data showing 99.1% efficacy at six months and 98.8% at 28 days, confirming the vaccine’s durability.

Importantly, the vaccine was well tolerated, with no safety concerns identified during the trial.

XTALKS WEBINAR: Enhancing Distributed Manufacturing and Vaccine Distribution through Blow-Fill-Seal Prefilled Drug Delivery Platforms

Live and On-Demand: Thursday, February 27, 2025, at 1pm EST (10am PST)

Register for this free webinar to learn critical considerations for improving global vaccine and healthcare delivery and outcomes. This webinar draws on the evolving concept of “access” in vaccine delivery in both high- and low-income countries.

Valneva’s partnerships with the Coalition for Epidemic Preparedness Innovations (CEPI), bolstered by a $41.3 million grant and funding from the European Union (EU), have supported expanded access initiatives. This includes post-marketing studies, label extensions for younger populations and a licensing agreement with the Serum Institute of India to supply the vaccine in Asia at affordable prices.

Last month, CEPI launched the ACHIEVE study, which plans to screen over 10,000 people in East Africa for chikungunya. By gathering data in regions where testing is limited and cases may be underreported, the study plans to inform future vaccine strategies and public health planning.

IXCHIQ has already been approved for adults in the US, Europe and Canada, and regulatory approval for adolescents and endemic populations is expected soon.

Approval in Brazil would mark the vaccine’s first use in a region where chikungunya is widespread.

Valneva is also advancing its investigational Lyme disease vaccine candidate, VLA15, currently in Phase II clinical development. Developed in collaboration with Pfizer, VLA15 recently had positive booster dose results and is expected to progress to Phase III trials. With FDA Fast Track designation, it remains the only Lyme disease vaccine candidate in advanced clinical trials.