Valneva's VLA1553 (Ixchiq), the first FDA-approved vaccine for chikungunya virus, continues to demonstrate sustained antibody persistence two years after a single-dose administration, according to results from a phase 3b trial. The open-label study (NCT04838444) provides further evidence of the vaccine's potential to offer long-term protection against the debilitating disease.
The chikungunya virus, transmitted through mosquito bites, poses a significant health risk in Africa, Asia, parts of Europe, and the Americas. While symptoms can range from mild, including rash, headache, and muscle pain, to acute, with high fever, intense myalgia, and polyarthralgia, approximately 43% of those infected develop chronic arthralgia that can persist for months or years.
The phase 3b trial enrolled 375 participants who were previously part of the VLA1553-301 clinical trial (NCT04546724). Participants received a single dose of VLA1553 and were followed for up to 10 years to assess antibody persistence and long-term safety. The primary objective was to evaluate antibody persistence annually from years 1 to 10 post-immunization, while the secondary objective focused on long-term safety over 6 months to 2 years.
Sustained Seroprotection
The study revealed that chikungunya virus-neutralizing antibodies remained above the protective threshold in a high proportion of participants for up to two years following vaccination. Seroprotection rates were 98.9% (356 of 360 participants) at the 1-year follow-up and 96.8% (306 of 316 participants) at the 2-year follow-up. These rates were consistent across age groups, with similar results observed in participants aged 18-64 years and those 65 years and older.
Safety Profile
No significant safety concerns were identified during the study period. Although 10 serious adverse events occurred in 9 participants (2%) between 6 months and 2 years, including one death due to a drug overdose, none were deemed related to the VLA1553 vaccination. Immunogenicity will continue to be monitored for at least 5 years.
Implications for Endemic Areas and Travelers
The investigators highlighted the importance of sustained antibody persistence given the unpredictable nature of chikungunya virus epidemiology. The findings suggest that VLA1553 could be particularly beneficial for individuals traveling internationally to endemic regions. According to the researchers, VLA1553 continues to demonstrate promise as a chikungunya virus vaccine for active immunization of individuals residing in or traveling to areas where the virus is prevalent.
