Ebola virus vaccines: Where do we stand?

The recent outbreak of Ebola virus disease in West Africa has led to more than 11,000 deaths, with a peak in mortality from August through December of 2014. A meeting convened by the World Health Organization (WHO) in September 2014, concluded that an urgent unmet need exists for efficacy and safety testing of the Ebola virus vaccine candidates and that clinical trials should be expedited. These vaccines could be used both in an outbreak setting and to provide long-term protection in populations at risk of sporadic outbreaks. A number of vaccines have been evaluated in phase 1 trials, but the two most advanced first-generation Ebola vaccine candidates are the live replicating vesicular stomatitis virus (rVSV) and the replication-defective chimpanzee adenovirus 3 (ChAd3). This review focuses on these two vaccines in clinical development and discusses the future opportunities and challenges faced in the licensure and deployment of Ebola virus vaccines.