Zika Vaccine Development: Flavivirus Foils

The current Zika virus outbreak has galvanized the public health community, resulting in rapid action by entities ranging from the World Health Organization to the United States government. The rapid response to Zika is perhaps the first of its kind, and it undoubtedly has been made possible by the lessons learned from the response to the 2014 Ebola virus outbreak in West Africa. However, Zika virus is not Ebola virus. As of February 2016 there were only 296 publications on Zika in the PubMed database, and a large number of these publications were commentaries or reviews lacking primary research data. In contrast, work had been underway for decades on the development of an Ebola virus vaccine, laying the groundwork for a rapid response in 2014. The broader communitys extensive experience with Dengue virus vaccine development and with the pros and cons of different vaccine platforms has led to speculation that a Zika virus vaccine can be accelerated, potentially with clinical trials initiating by the end of 2016 1,2. However, there are unique attributes of Zika virus, as well as many unanswered questions about the virus, that should be considered before a potential vaccine is administered to the public.Perhaps the best understood aspect of Zika virus is its close relation to Dengue virus and other flaviviruses. The close phylogenetic relationship between the flaviviruses has confounded diagnostic efforts as antibody elicited by viruses in this family cross-react 3,4. Definitive diagnosis of Zika infection in individuals with previous flavivirus infection requires detection of viral RNA by PCR, which is only achievable during approximately a two week window early in infection. Efforts are underway to develop serological assays to distinguish the flavivirus infections 5, which would significantly advance our understanding of the epidemiology of Zika virus. However, the cross-reactivity of antibody elicited by Dengue and Zika is more than a diagnostic inconven