Breakthrough Chikungunya Single-dose Vaccine Success In Phase Iii Trials

Phase III trials for the VLA1553 vaccine against chikungunya virus indicated promising results by inducing protective CHIKV neutralizing antibody titers within 28 days of the single-dose. VLA1553 is currently the only promising candidate in Phase III trials targeting long term protection against chikungunya.

French vaccine developer, &Valneva, announced positive results from Phase III trials of their single-dose chikungunya vaccine VLA1533, which exceeded the US FDA 70% protection threshold, reaching levels of 98.5% seroprotection. As such, the program has been awarded Breakthrough Designation status by the FDA, holding promise for the world’s first single-dose vaccine providing long-term protection against chikungunya virus (CHIKV).

CHIKV is a Togaviridae virus transmitted by infected female &Aedes &mosquitoes, inducing abrupt onset of fever and joint pain. The most common vector is &Aedes aegypti &in prominent tropical regions, generally circulating in low- and middle-income countries. Less commonly &Aedes albopictus &is associated with transmission in temperate regions such as Italy. The virus is a major threat to public health as despite low mortality rates, the morbidity remains high due to outbreaks typically affecting 30-70% of populations in circulating regions. VLA1553 could save many lives and reduce morbidity as there are currently no preventative vaccines or treatments, if the vaccine is approved.

Valneva and the Brazilian institute &Instituto Butantan &have collaborated to develop the vaccine, and potentially manufacture and distribute the vaccine should the follow-up continue to be successful. The VLA1553 Phase III trial included 4115 adults aged ≥& 18 years across 44 test sites in the United States. Twenty-eight days after the participants received the single-dose vaccine, 98.5% were found to have CHIKV neutralizing antibody titers induced by the vaccine. Interestingly, the Phase III trial also revealed that the vaccine induced equally high neutralizing antibody titers in all age groups, indicating VLA1553 is highly immunogenic in elderly participants as well as younger adults.

Juan Carlos Jaramillo, Chief Medical Officer of Valneva commented, “We are delighted with these Phase III results confirming the compelling profile of our vaccine candidate across all age groups. These first-ever Phase III trial results for a chikungunya vaccine mean that we are a step closer to addressing this major, growing and unmet public health threat. I would like to thank everyone who participated in the trial and who continued to advance the trial during the pandemic. We will continue to work with regulators to bring VLA1553 to market as soon as possible.”

Phase I of the trial concluded that VLA1553 has a good safety profile as the vaccine was generally well tolerated among the 3082 participants it evaluated for safety. Since this Phase, the independent Data Safety Monitoring Board have not identified any safety concerns. Similarly, the Phase III trial had a consistent safety profile with the majority of solicited systemic adverse events being mild or moderate and resolved within 3 days, with approximately 50% of study participants reporting headache, fatigue and myalgia. Only 1.6% of study participants reported severe adverse events such as fever.

The trial will continue to the final analysis on the 6-month safety data, releasing the final results within the next 6 months. The roll-out of VLA1553 will be a health priority for many countries, which is reflected in the programs potential eligibility for a Priority Review Voucher and will be awarded to the sponsor of the first chikungunya vaccine approved in the USA.