Valneva Reports Positive Results for Phase 1 Trial of Second-Generation Zika Vaccine Candidate
November 4, 2025 – BioManufacturing, Biotechnology, Clinical Trials, Drug Delivery, Other, Pharmaceutical – Valneva, Zika virus, clinical trials, infectious diseases, vaccine development, vaccines
Immune response successfully improved with second generation vaccine candidate
4 November 2025 — Saint-Herblain, France — Valneva SE, a specialty vaccine company, today announced positive results of its Phase 1 clinical trial investigating the safety and immunogenicity of VLA1601, its second-generation adjuvanted inactivated vaccine candidate against the Zika virus (ZIKV).
The randomized controlled Phase 1 trial, VLA1601-102, enrolled approximately 150 participants aged
18 to 49 years in the United States. Participants received two administrations, four weeks apart, of a
low, medium or high dose of the highly purified inactivated aluminum-adjuvanted vaccine candidate
VLA1601. In addition, the low dose of VLA1601 was evaluated with additional adjuvants, either the CpG
1018® adjuvant from Dynavax Technologies Corporation or the 3M-052-AF adjuvant from the Access
to Advanced Health Institute (AAHI).
Data up to Day 57 (four weeks after the second dose (Part A Analysis)) showed that VLA1601 was
generally safe and well tolerated in all five treatment arms, and no safety concerns were identified.
Additionally, an independent Data Safety Monitoring Board did not reveal any safety issues.
Two doses of VLA1601 were immunogenic across all five treatment arms investigated (i.e., alumadjuvanted Low, Medium and High antigen dose; Low with additional adjuvants). The strongest immune response was observed in the double-adjuvant treatment arms (Low+alum+3M-052-AF and
Low+alum+CpG1018) with statistically significantly higher neutralizing antibody titers (Geometric Mean
Titers – GMTs) at Day 43 and Day 57 than in the single-adjuvant (alum) treatment arm.
The immune response induced by the double-adjuvanted VLA1601 second generation vaccine
candidate was successfully improved compared to the first-generation vaccine candidate with higher
peak seroconversion rates (>93% vs 86%) and peak Geometric Mean Fold Increase of titers (>56 fold
vs >7 fold). Phase 1 results from Valneva’s first-generation Zika vaccine candidate were reported in
2018.
VLA1601 is developed on the original manufacturing platform of Valneva’s licensed Japanese
encephalitis vaccine IXIARO, which was further optimized to develop the Company’s inactivated,
adjuvanted COVID-19 vaccine VLA2001.
Juan Carlos Jaramillo M.D., Chief Medical Officer of Valneva, 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.”
Despite the medical need, regulatory pathways and market opportunities for potential Zika vaccines
remain uncertain. Valneva will therefore only consider further potential development steps for VLA1601
if concrete major private and public funding opportunities materialize.
About Valneva SE
We are a specialty vaccine company that develops, manufactures, and commercializes prophylactic
vaccines for infectious diseases addressing unmet medical needs. We take a highly specialized and
targeted approach, applying our deep expertise across multiple vaccine modalities, focused on
providing either first-, best- or only-in-class vaccine solutions. We have a strong track record, having
advanced multiple vaccines from early R&D to approvals, and currently market three proprietary travel
vaccines. Revenues from our growing commercial business help fuel the continued advancement of
our vaccine pipeline. This includes the only Lyme disease vaccine candidate in advanced clinical
development, which is partnered with Pfizer, the world’s most clinically advanced Shigella vaccine
candidate, as well as vaccine candidates against the Zika virus and other global public health threats.
More information is available at www.valneva.com.
