Long term prospects for a vaccine against Zika virus hold promise but imminent expectation should be tempered by reality

The rapid rise in the number of reported clinical cases of Zika in South and Central America over the span of a few months in late 2015 and early 2016 presents a real risk of a global epidemic of this Aedes mosquitotransmitted viral infection. This threat is exacerbated by the globalisation of the human population which promotes the movement of asymptomatic carriers between nations in the same or separate continents. Pregnant women are considered at highest risk since microcephaly in the developing foetus is strongly associated with, if not yet proven as caused by, Zika infection. The possibility of additional modes of virus transmission, vertical and sexual, if confirmed, suggests the life cycle of the virus to be very complex and thus limits the scope of predictive models, which in turn may impede control efforts. Currently, no anti-Zika vaccine is available and while this has now been prioritised by multiple funding agencies, it may take several years to come to commercial fruition. The fact that Zika is closely related to yellow fever and Japanese encephalitis viruses, for both of which effective vaccines exist, offers hope that the fast-tracked preparation of a candidate vaccine is feasible. However, performing clinical trials on pregnant women would provide ethical and practical challenges to overcome before licensure is granted for administration to the general public. In the meantime, alternative public health management strategies, such as vector control programs to target mosquito breeding, are required in order to limit the global spread of this re-emerging disease.