Key Takeaways
- Strong pediatric response: Valneva’s single-dose chikungunya vaccine, Ixchiq, demonstrated a 96.5% seroresponse rate at six months in chikungunya-naïve children aged one to 11 years, supporting use of the full dose in this population.
- Clean safety profile in children: Both full and half doses were well tolerated in the Phase II pediatric trial, with no safety concerns reported, aligning with prior adult and adolescent data.
- Next steps toward label expansion: The results are expected to support a Phase III trial in children starting in Q1 2026 as Valneva seeks to extend Ixchiq’s label to younger age groups.
Results from the Phase II VLA1553-221 trial show that Ixchiq, Valneva’s single-shot chikungunya vaccine, demonstrated strong six-month safety and antibody persistence results in children aged between one and 11 years. The trial was partially funded by the Coalition for Epidemic Preparedness Innovations, with additional support provided by the European Union.1
How did Valneva’s Chikungunya Vaccine Perform in Children?
“The six months persistence and safety data in children are aligned with the robust antibody response and safety profile we reported in adolescents after a single vaccination,” said Juan Carlos Jaramillo, MD, chief medical officer, Valneva, in a press release.
Trial Details and Dosing Strategy
The multi-center, randomized, observer-blinded, dose-response VLA1553-221 trial included 304 healthy children from one to 11 years of age across three sites in the Dominican Republic and Honduras. Patients were randomly assigned in a 2:2:1 to receive either a full dose, half dose, or an active control (Nimenrix). The primary and secondary endpoints of the trial aimed to evaluate the safety and immunogenicity of the full dose as well as the half dose of the vaccine.
Six-Month Immunogenicity and Safety Results
Results show a 96.5% seroresponse rate in chikungunya-naïve children who were given the full dose at day 180. Additionally, the full dose demonstrated a more notable immune response at both day 15 and day 180 compared to the half dose. Both dose levels were well tolerated, with no safety concerns reported. The findings also align with previous adult and adolescent data.1
Regulatory Concerns in Older Populations
Last month, the FDA and the Centers for Disease Control and Prevention (CDC) jointly recommended pausing the use of Ixchiq in seniors in the United States as a result of investigations into serious adverse events (SAEs). As of May 7, 2025, 17 SAEs have been reported, which included two deaths, in individuals between 62 and 89 years of age who received Ixchiq.2
Global Spread and Public Health Implications
According to Valneva, chikungunya began a rapid spread in 2004, having been identified in 110 countries across Asia, Africa, Europe, and the Americas. From 2013 to 2023, an estimated 3.7 million cases were reported in the Americas.1 According to the CDC, a total of 28 cases per year were reported in US citizens who recently returned from affected areas in Asia, Africa, or the Indian Ocean between 2006 and 2013. Local transmission was eventually identified, although no cases of local transmission have been reported since 2019. An estimated 60 million people living in the United States travel to countries in which mosquito-borne diseases such as chikungunya are endemic annually.2
As a result of climate change, the medical and economic burden of the virus is expected to grow due to mosquito vectors that transmit the disease spreading globally.1
“Considering the significant risk chikungunya poses to individuals living in or traveling to endemic areas, it’s crucial to ensure that the vaccine is accessible to people of all ages and capable of potentially offering long-term protection from a single shot,” continued Jaramillo, in the press release. “This is especially important in Low- and Middle-Income countries where access to vaccines is often limited.”
Next Steps for Pediatric Development
Moving forward, the results from the trial are expected to support a Phase III study in pediatric patients, which is expected to begin in the first quarter of next year. Ixchiq was first granted accelerated approval in November 2023 based on results from two studies in 3,500 individuals over 18 years of age with an increased risk of exposure to the virus in North America.1
References
1. Valneva Reports Positive Six-Month Antibody Persistence and Safety Phase 2 Results in Children for its Single-Shot Chikungunya Vaccine IXCHIQ®. Valneva. June 5, 2025. Accessed June 9, 2025. https://valneva.com/press-release/valneva-reports-positive-six-month-antibody-persistence-and-safety-phase-2-results-in-children-for-its-single-shot-chikungunya-vaccine-ixchiq/
2. FDA, CDC Recommend Pause on Valneva's Chikungunya Vaccine for Seniors. PharmExec. May 14, 2025. Accessed June 9, 2025. https://www.pharmexec.com/view/fda-cdc-recommend-pause-valneva-chikungunya-vaccine-seniors
