Valneva’s Double-Adjuvanted Zika Vaccine Shows Strong Safety And Immune Response In Phase 1 Study

Valneva SE announced positive Phase 1 results for its second-generation Zika virus vaccine candidate, VLA1601. The randomized, controlled trial enrolled around 150 adults aged 18 to 49 in the U.S. and evaluated low, medium, and high doses of the inactivated, aluminum-adjuvanted vaccine, with two administrations four weeks apart. The low-dose group was also tested with additional adjuvants—CpG 1018® from Dynavax Technologies and 3M-052-AF from the Access to Advanced Health Institute (AAHI).

The results up to Day 57 showed that VLA1601 was safe and well-tolerated across all five treatment arms, with no safety issues reported by the Data Safety Monitoring Board. Two doses generated strong immune responses, with the double-adjuvanted formulations achieving significantly higher neutralizing antibody titers compared to the single-adjuvant version. The double-adjuvant vaccines also achieved higher seroconversion rates (over 93%) and geometric mean fold increases in titers (>56-fold), representing a marked improvement over Valneva’s first-generation Zika vaccine tested in 2018.

Developed using the same manufacturing platform as Valneva’s approved Japanese encephalitis vaccine, IXIARO®, VLA1601 leverages innovations from the company’s COVID-19 vaccine VLA2001. Chief Medical Officer Dr. Juan Carlos Jaramillo highlighted the importance of the findings amid the growing threat of mosquito-borne diseases driven by climate change. However, Valneva noted that future development of the vaccine will depend on securing substantial public or private funding due to ongoing regulatory and market uncertainties surrounding Zika vaccines.