An experimental Ebola vaccine developed by US company NewLink Genetics will start clinical trials within the next few days, according to the World Health Organisation (WHO).
The news comes as the first case of Ebola to be diagnosed on US soil – Liberian national Thomas Duncan – is fighting for his life at the Dallas hospital where he is being held in isolation. The US Centers for Disease Control and Prevention (CDC) is continuing to monitor people who came into contact with Duncan prior to his hospitalisation.
NewLink’s rVSV-ZEBOV candidate is one of two candidate vaccines being tested with the involvement of the WHO, along with GlaxoSmithKline’s chimpanzee-derived cAd3-ZEBOV vaccine that started trials in the UK and US last month.
The NewLink vaccine – based on a weakened vesicular stomatitis virus (VSV) – was developed by the Public Health Agency of Canada in Winnipeg and will start a phase I trial at the US National Institute of Allergy and Infectious Diseases (NIAID) in the next few days, said the WHO.
The WHO said the government of Canada has donated 800 vials of rVSV-ZEBOV to the effort and – once data on dosing from phase I trials become available – this could be enough material to supply 1,500 to 2,000 doses of vaccine.
At the end of September the WHO convened a meeting of vaccine experts to decided how best to accelerate the trials programme for the two clinical-trade candidates, truncating the usual timeframe for testing “from two to four years [to] a matter of months.”
In particular, the group examined what must be done to move quickly beyond safety testing in human volunteers to phase II trial designs that will test the two vaccines’ ability to provide protection against Ebola infection.
Both candidates have limitations that will hamper their development and use, not least a requirement that they are stored at -80°C which could pose significant logistical problems for distribution. The amount of material available for testing is also a key limitation, although both companies have said they are stepping up production and are anticipating “a very significant increase in scale during the first half of 2015,” according to the WHO.
The experts noted that while a conventional randomised controlled trial would be the preferred option, it may be possible to consider alternative designs such as the “randomised stepped wedge” model. This is an adaptive trial design that draws on experience with those first receiving an intervention and applies it to those treated later.
“Such a design makes it possible to roll out vaccinations and evaluate efficacy at the same time,” said the WHO, which has previously backed the use of untested drugs to treat Ebola given the unprecedented scale of the outbreak.
The agency said it expects to have developed the protocol design for the phase II vaccine studies by October/November 2014 and hopes to start efficacy trials in January/February 2015. Johnson & Johnson (J&J) has also fast-tracked the development of vaccines for the virus, but is not expected to have material ready for clinical trials until early 2015.
No threat that Ebola is airborne
Ahead of the weekend, the WHO issued a statement emphasising that in contrast to recent media reports there is as yet no evidence that the Ebola virus strain circulating in the outbreak has mutated to allow airborne transmission.
“The Ebola virus only spreads through contact with bodily fluids,” it said. “Viruses do mutate but it is a complex process that takes time.”
The agency stressed however that there are real risks and concerns with an outbreak of this scale, with more than 3,400 deaths out of 7,470 confirmed or suspected cases as of October 3.
“Every day more people are becoming infected and more are dying because they cannot get the care they need,” said the WHO.
“Energy needs to be focused on swiftly addressing the real needs and gaps in communities affected by this disease.”