Valneva has reported encouraging results from a Phase I clinical trial assessing the immunogenicity and safety of its second generation Zika vaccine candidate, VLA1601.
VLA1601 is a vaccine that has been purified and inactivated, specifically designed to combat the Zika virus (ZIKV).
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The controlled and randomised VLA1601-102 study enrolled around 150 subjects aged 18 to 49 years in the US.
All subjects received two doses of VLA1601, administered four weeks apart, at high, low, or medium doses, accompanied by an aluminium-adjuvanted vaccine.
Additionally, the vaccine’s low dose was assessed with additional adjuvants 3M-052-AF or CpG1018 sourced from the Access to Advanced Health Institute and Dynavax Technologies, respectively.
Data gathered up to day 57 after the second dose indicated that VLA1601 was generally well tolerated and safe across all five treatment groups.
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By GlobalDataNo safety concerns were identified and an independent Data Safety Monitoring Board did not report any safety concerns.
The vaccine candidate demonstrated immunogenicity across all tested groups, with the double-adjuvant arms (low dose combined with alum and either CpG1018 or 3M-052-AF) producing statistically significantly higher neutralising antibody titres on days 43 and 57 in comparison to the single-adjuvant arm.
Valneva’s second-generation vaccine candidate showed an improved immune response over its first generation, including peak geometric mean fold increase of titers over 56-fold and a peak seroconversion rate above 93%.
Results from the first-generation Phase I trial were previously reported in 2018.
VLA1601 builds on the original manufacturing platform of the company’s licensed Japanese encephalitis vaccine Ixiaro.
Valneva chief medical officer Juan Carlos Jaramillo said: “We are pleased by the notable safety and immunogenicity results demonstrated for our Zika vaccine candidate and especially our double-adjuvantation results.
“As global temperatures rise and rainfall patterns shifts, the expanding habitat of disease-carrying mosquitoes poses a growing public health challenge for infections such as Zika.”
In June 2025, Valneva reported encouraging six-month safety and antibody persistence data from the multi-centre Phase II trial, VLA1553-221, of its chikungunya vaccine, Ixchiq, in 304 healthy paediatric subjects aged between one and 11 years.
