94% of participants maintained seroresponse five years after a single vaccination

Comparable antibody persistence observed in older (65+) and younger adults

Data further reinforce IXCHIQ^®'s differentiated profile with durable antibody persistence against an unpredictable outbreak disease

Valneva SE (Nasdaq: VALN; Euronext Paris: VLA), a specialty vaccine company, reported positive five-year antibody persistence data for its single dose chikungunya vaccine IXCHIQ^®. The results demonstrate durable antibody persistence across all age groups evaluated and are consistent with previously reported persistence results^1,2,3,4. The results are in line with Valneva’s expectations for this vaccine, further supporting IXCHIQ^®'s differentiated profile and its potential to provide long-term protection following a single vaccination, similarly to other live-attenuated vaccines⁵⁶.

Among the 221 healthy adults who were evaluable at Year 5, 94% maintained neutralizing antibody titers well above the seroresponse threshold⁷ five years after the single-dose vaccination. Antibody persistence in older adults aged 65 years and above was comparable to that observed in younger adults aged 18 to 64 years, with similar geometric mean titers (GMTs) and seroresponse rates (SRRs).

Hanneke Schuitemaker, Ph.D., Chief Scientific Officer of Valneva, commented, “These five-year data further reinforce IXCHIQ^®'s unique value proposition. For diseases such as chikungunya, where outbreaks are difficult to predict, durable immune persistence following a single dose represents a significant public health advantage. This is particularly important not only for travelers, but also for populations living in endemic regions, many of which are in low- and middle-income countries where access to healthcare and vaccination may be more limited.”

Trial VLA1553-303 received funding support from the Coalition for Epidemic Preparedness Innovations (CEPI) and the European Union's Horizon Europe program. Under the study protocol, participants will continue to be followed for up to ten years after vaccination to further characterize the long-term durability of immune responses generated by IXCHIQ^®.

Valneva is also continuing to generate real-world evidence for IXCHIQ^® through several post-marketing studies and initiatives, including a Pilot Vaccination Strategy (PVS) in Brazil, the first large-scale public vaccination campaign using IXCHIQ^®. Conducted between February and October 2026 by the Brazilian Ministry of Health and Instituto Butantan, with support from Valneva, the campaign vaccinated nearly 80,000 adults aged 18 to 59 years. The PVS serves as the foundation for ongoing post-marketing studies^6-8, which are expected to generate important effectiveness and safety data and further support the vaccine's public health value.