On 1 February 2016, the World Health Organization (WHO) declared a Public Health Emergency of International Concern (PHEIC) following the unusual incidence of Zika virus (ZIKV) disease and the strong association, in time and place in Latin America and the Caribbean, between ZIKV infection and a rise in cases of congenital malformations, particularly microcephaly, and neurological complications.
Following the declaration of PHEIC, the development a ZIKV vaccine assumed high priority. Vaccine clinical development was refined as understanding of pathogenesis and disease dynamics evolved, and new diagnostic and serological assays are being developed.
The WHO vaccine pipeline tracker currently registers 45 ZIKV vaccine candidates under development, by private and public-sector developers. Six of these candidates have entered clinical trials. Under the Blueprint Plan of Action, WHO has led a series of initiatives to maintain continuous dialogue between developers, regulators and public health experts to identify how best to achieve rapid, robust, safe, and evidence-based licensing of ZIKV vaccines.
In March 2017, the WHO Global Coordination Mechanism for Research and Development reviewed the ZIKV vaccine development pipeline, and called for improved collaboration and coordination to accelerate ZIKV vaccine evaluation.
On June 1-2, 2017, the WHO convened a group of about 30 experts in epidemiology, regulatory, preclinical and clinical vaccine trials, and mathematical modelling, in a workshop on planning for Zika vaccine efficacy trials. The workshop aimed to define generic principles on how to best design, conduct and analyze vaccine trials against ZIKV, based on the best available scientific evidence as well as on lessons learned from evaluating other flavivirus vaccines. The workshop builds on WHO efforts in Zika vaccine R&D.
Participants reviewed available evidence, identified and discussed methodological options to evaluate vaccines, regardless of vaccine products, and agreed on some preliminary recommendations. It was recognised both that the preliminary recommendations are likely to evolve as new evidence is generated and also, they must be tailored to the social and cultural context of affected communities.