Zika vaccine: early data demonstrate safety, immunogenicity

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  • Preliminary data show that a purified formalin-inactivated Zika virus (ZIKV) vaccine (ZPIV) has a good tolerability profile, and provides sufficient immunogenicity to offer clinical protection against ZIKV.
  • Initial data support larger, more advanced trials to further establish clinical benefit.

Why this matters

  • Although ZIKV outbreaks are mostly over, the threat of resurgent and unpredictable epidemics remains; reports continue to evolve documenting viral shedding and persistence, as well as poor congenital outcomes.
  • Clinicians should continue to counsel patients suspected of ZIKV exposure or planning to become pregnant on prevention, sexual transmission, and fetal outcomes.

Key results

  • 67 individuals vaccinated with 2 ZPIV doses, 12 with placebo, followed to day 57.
  • No clinically meaningful adverse events (AEs) were reported (84% [n=56] reported 1 AEs after first, second, or both doses; most were mild/moderate).
  • Neutralizing antibodies were elicited in almost all participants at 2-4 weeks after second dose.
  • Primary immunogenicity endpoint (geometric mean titers) reached peak by day 43; 92% (n=48) seroconverted after second dose at peak 1:10 threshold.

Study design

  • Aggregate analysis of 3 single-center, placebo-controlled, double-blind trials to determine safety, immunogenicity of ZPIV in flavivirus-naive (infection or vaccination) adults.
  • Funding: Departments of the Army and Defense; National Institute of Allergy and Infectious Diseases.


  • Short-term follow-up.