In June 2023 Valneva announced the publication of Phase III data for its single-shot chikungunya vaccine candidate VLA1553. The article offers a detailed analysis of the Phase III results showing that VLA1553 demonstrated a “very high seroresponse rate of 98.9% in participants 28 days after receiving the single administration”. It was also “generally safe and equally well tolerated” in younger and older adults.  


The article explains that chikungunya is a mosquito-transmitted disease that occurs in “sporadic, unpredictable outbreaks”. Due to “increasing international travel” and “spread of potential vectors” it has been identified in over 100 countries worldwide. Symptoms of chikungunya virus disease can include fever, joint pain, headache, or nausea. With a case-fatality rate of between 0.3 and 1 per 1000, most deaths occur in neonates, adults with underlying conditions, and older people.  

“There is an urgent medical need for prophylaxis against chikungunya virus infection, since neither specific treatment nor vaccine is available.” 

The vaccine candidate is a live-attenuated, single dose prophylactic vaccine that aims to target “all circulating chikungunya virus strains”. It is based on the La Reunion strain (LR2006-OPY1) of east central South African genotype.  

“VLA1553 is intended to rapidly trigger a protective, durable antibody titre.” 

In previous studies the candidate demonstrated “excellent immunogenicity” with 100% seroconversion from day 14. Although it was “generally safe in all dose groups” there was a higher incidence of adverse events and viraemia in the high dose group. However, it showed a “strong reduced viraemia in humans” compared to wild-type chikungunya virus.  

The study 

The paper reports that the study “met its primary endpoint”. 28 days after vaccination it induced seroprotective levels of antibodies in 98.9% of participants. High seroprotection rates were sustained up to 180 days after vaccination. Further data are being generated to monitor continued seroprotection as the researchers “expect this vaccine to induce long-lasting immunity”.  

The vaccine was “generally safe and well tolerated in all populations” following a single vaccination. An independent DSMB evaluated safety data for the duration of the study ad “did not identify any safety concerns”.  

VLA1553 is the only chikungunya vaccine candidate for which regulatory processes are underway, with a BLA under priority review by the USA FDA. A regulatory application has also been filed with Health Canada.  

Dr Juan Carlos Jaramillo, Valneva’s Chief Medical Officer, believes that the publication “underlines the strength of VLA1553’s scientific approach”. It is “consistent with the quality” of the study.  

“We are pleased that more detailed results on our single-shot chikungunya vaccine candidate are now available to the scientific and broader public health communities.”  

For more on this vaccine and other efforts by Valenva, check out our interview with Thomas Lingelbach here. To read the paper in full click here. Don’t forget to subscribe for regular insights!