The Ebola virus is classified into several subtypes, and the virus in question in West Africa is the Zaire Ebola virus. Untreated, the mortality rate from this subtype is 80 – 90 %, but survival can be somewhat improved by supportive care (2). In addition to attempting to combat the epidemic by contact tracing and isolation, it would be advantageous to be able to administer vaccines and to provide antiviral treatment. An expert panel discussion arranged by WHO on 11 August 2014 concluded that in this situation the initiation of experimental interventions on patients could be accepted for drugs that do not have a scientifically documented effect and that are not fully validated with regard to safety and adverse effects in humans. The expert panel set several requirements: such use was to follow the ethical rules (including informed consent), the distribution of such treatment had to be carried out fairly, and all data involved in the treatment were to be systematically gathered to enable professionals to learn from them (3). They did not explicitly mention that this should be done in the form of placebo-controlled clinical trials, even though – as was concluded in a subsequent commentary in The Lancet (4) – this is the best way of avoiding confounding factors.
A vaccine developed by GlaxoSmithKline (GSK) and the National Institute of Allergy and Infectious Diseases (NIAID) is now ready for phase 1 trials in the UK, Gambia and Mali as soon as ethical approval has been granted. It is hoped that the vaccine’s safety will be clarified before the end of this year so that clinical trials can then be initiated on populations in the areas at risk. This vaccine is based on a live viral vector, the chimpanzee adenovirus type 3 (ChAd3), with genetic material from the Ebola virus. According to a press release from GSK, studies on primates that were infected with the Ebola virus show promising protection (5).
Another promising Ebola vaccine platform, developed by the Public Health Agency of Canada among others, is based on the recombinant vesicular stomatitis virus (rVSV) (6). A trial of various rVSV vaccines provided 100 % protection against the Ebola virus pre-exposure in primates, but did not elicit cross-immunity between the Zaire Ebola virus and the Sudan Ebola virus (7). Surprisingly enough, the vaccines could also be used post-exposure. In experiments with the Marburg virus – a virus in the same taxonomic family as the Ebola virus – five out of six primates survived when the vaccine was administered 24 hours after they had been given a fatal dose of the virus, and two out of six survived when it was administered 48 hours afterwards (8).
Bavaria Nordic is also working on an Ebola vaccine, and is planning to start phase 1 studies in 2015 (9). The possibility of vaccinating healthcare workers, hygiene staff and infected contact persons against the Ebola virus will represent a large step forward, although time is against us in this particular epidemic. Ultra-fast ethical approval of the trials by WHO and national health authorities will be crucial.