Clinical data
IXCHIQ®Chikungunya vaccine (live) can provide an immune response up to two years
Please note, no efficacy data are available for IXCHIQ®. The clinical efficacy of IXCHIQ® was inferred from a post-vaccination CHIKV-specific neutralising antibody titre threshold. A threshold of CHIKV-specific neutralising antibody μPRNT50 titre of ≥150 was selected as surrogate marker for protection, referred to as seroresponse. This threshold was determined from a non-human primate passive transfer study in which animals with titres ≥150 were protected against wild-type CHIKV infections and had undetectable virus in blood during 14 days after the challenge. In addition, the threshold was supported by data obtained from a prospective human sero-epidemiological study.1
The threshold of 150 was defined conservatively as a surrogate endpoint for protection and considered by both the FDA and EMA to be reasonably likely to predict clinical benefit.4,5
In a pivotal phase III trial*, a single dose of IXCHIQ® induced a seroresponse† in 98.9% of participants (n=266) after 28 days (95% CI 96.7–99.8; p<0.0001). In a Phase IIIb trial involving the same patients (n=316), seroresponse rate was 96.8% (95% CI 94.3–98.5) after 24 months.1,4,5
*Phase III trial was a multicentre, randomised, placebo-controlled, double-blinded pivotal study to evaluate safety and immunogenicity of IXCHIQ® vaccine in 4128 participants across 43 professional vaccine trial sites in the US (266 patients in the IXCHIQ® arm made up the immunogenicity test population).4
†Defined as CHIKV neutralising antibody titre ≥150 by μPRNT50 (50% reduction in a micro plaque reduction neutralisation test) for baseline participants 28 days after first vaccination. The lower bound of the 95% CI for the SRR at Day 29 in IXCHIQ® group needed to exceed 70% neutralising antibody titres determined using μPRNT50 assay.1,4
Safety profile
In the Phase III clinical trial, most adverse reactions were mild to moderate and most resolved in 2–3 days.*4 In pooled safety data from three completed Phase I and Phase III studies†, the most common vaccination site reactions were tenderness (10.8%) and pain (6.1%). The most common systemic reactions were:1
The full list of adverse drug reactions is as follows:†1
Adverse reactions are listed according to the following frequency categories: very common: ≥ 1/10; common: ≥ 1/100 to < 1/10; uncommon: ≥ 1/1000 to < 1/100; rare: ≥ 1/10 000 to < 1/1000; very rare: <1/10 000.
*Data from the landmark Phase III trial of 4128 participants at 43 study sites (safety population consisted of 4115 individuals).4
†Data from the pooled safety data from three completed Phase I and III clinical studies conducted in the US on 3610 participants ≥18 years old who received one dose of IXCHIQ® with a follow-up of six months.1
‡Includes: leukopenia (leukocyte decreased), neutropenia (neutrophil decreased) and lymphopenia (lymphocyte decreased).
§Includes: Alanine aminotransferase increased (ALT) and Aspartate aminotransferase increased (AST).
Please refer to the summary of product characteristics for more information on undesirable effects.
References
- IXCHIQ. Summary of Product Characteristics. February 2026. Available at: https://www.medicines.org.uk/emc/product/100652/smpc. Accessed: March 2026.
- Paixão, E.S., Rodrigues, L.C., Costa, M. da C.N., et al. Chikungunya chronic disease: a systematic review and meta-analysis. Trans R Soc Trop Med Hyg. 2018;112(7):301–316.
- World Health Organization. Chikungunya fact sheet. April 2025. Available at: https://www.who.int/news-room/fact-sheets/detail/chikungunya. Accessed: March 2026.
- Schneider, M., Narciso-Abraham, M., Hadl, S., et al. Safety and immunogenicity of a single-shot live-attenuated chikungunya vaccine: a double-blind, multicentre, randomised, placebo-controlled, phase 3 trial. Lancet. 2023;401(10394):2138–2147.
- McMahon, R., Toepfer, S., Sattler, N., et al. Antibody persistence and safety of a live-attenuated chikungunya virus vaccine up to 2 years after single-dose administration in adults in the USA: a single-arm, multicentre, phase 3b study. Lancet Infectious Diseases. 2024;24(12):1383–1392.
Reporting forms and information can be found at www.mhra.gov.uk/yellowcard or search for MHRA Yellow Card in the Google Play or Apple App Store. Adverse events should also be reported to the Valneva UK Ltd Medical Information department on Tel: 01506 446608 or via email: safety@valneva.com