Chikungunya virus virus-like particle vaccine (Vimkunya) induces a rapid and durable antigen-specific CD4+ T cell response.

Chikungunya virus (CHIKV), a single-stranded, positive-sense RNA alphavirus, is transmitted to humans by infected Aedes mosquitoes. It poses an emerging threat to public health in Aedes-endemic countries and a growing risk to travelers visiting these countries. Typical acute symptoms include fever, arthralgia, rash, myalgia, fatigue and headache. In over 40% of cases, these symptoms can progress into chronic disease, primarily characterized by debilitating arthralgia. CHIKV vaccine (Vimkunya, Bavarian Nordic) is an aluminum hydroxide-adjuvanted virus-like particle (VLP) vaccine recently approved in the United States, European Union, and United Kingdom for the prevention of CHIKV disease in individuals aged 12 years and above. Phase 3 results showed a favorable safety profile and high immunogenicity, with antibody responses starting to build as early as eight days after immunization. Here, we evaluated whether Vimkunya is also able to induce CHIKV-specific T cell responses. Responses were assessed in longitudinal clinical samples from vaccinated individuals (N = 30) at five time points (day 1 pre-immunization, and days 8, 29, 57, and 182 post-immunization) using activation-induced marker (AIM) assays. Comparable to the antibody responses, CHIKV-specific CD4+ T cells were detected as early as eight days post-vaccination, with their frequency increasing over 57 days and stabilizing until 182 days. These results support the rapid induction and durability of the immune response elicited by Vimkunya, thereby supporting this vaccine's potential to provide protection against CHIKV disease.