Persistence of Immunogenicity of a Purified Inactivated Zika Virus Vaccine Candidate in Healthy Adults: 2 Years of Follow-up Compared With Natural Infection.

Background: We report 2-year persistence of immune response to Takeda's prophylactic purified formalin-inactivated whole Zika virus vaccine candidate (TAK-426) compared with that observed after natural infection.
Methods: A randomized, observer-blind, placebo-controlled, dose-selection, phase 1 trial was conducted in 18-49-year-old adults at 9 centers (7 in the United States, 2 in Puerto Rico) from 13 November 2017 to 24 November 2020. Primary objectives were safety, tolerability, and immunogenicity of 3 increasing doses of TAK-426 administered as 2 doses 28 days apart to flavivirus (FV)-naive and FV-primed adults. Here, we report on safety and persistence of immunity up to 2 years after primary vaccination with 10-μg TAK-426, the highest dose, and compare neutralizing antibody responses with those observed after natural infection.
Results: TAK-426 at 10-μg had an acceptable safety profile in FV-naive and FV-primed adults up to 24 months after dose 2. Seropositivity for neutralizing antibodies was 100% at 1 year, and 93.8% and 76.2% at 2 years in FV-naive and FV-primed groups, respectively. TAK-426 responses were comparable in magnitude and kinetics with those elicited by natural Zika virus infection.
Conclusions: These results support the further clinical development of TAK-426 for both FV-naive and FV-primed populations.
Clinical Trials Registration: NCT03343626.
Competing Interests: Potential conflicts of interest. C. J. A., F. N., K. J. M., K. B., P. K., M. L., E. W., T. D. P., W. R. B., J. S., and G. D. are employees of Takeda and hold stock/stock options in Takeda. H. H. H., H. P., F. P., and V. M. were employees of Takeda when the study was conducted and may hold stock/stock options in Takeda. E. J. A. reports consultancy for Janssen, Medscape, Pfizer, Sanofi Pasteur, GlaxoSmithKline, and Moderna; safety monitoring boards for Kentucky BioProcessing, Sanofi Pasteur, and WCG and ACI Clinical; institutional clinical research funding from GlaxoSmithKline, Janssen, MedImmune, Merck Sharp & Dohme, Micron, PaxVax, Pfizer, Regeneron, and Sanofi Pasteur; and institutional funding from the National Institutes of Health for clinical research on Moderna and Janssen vaccines. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.
(© The Author(s) 2022. Published by Oxford University Press on behalf of Infectious Diseases Society of America.)