Scientists at Oxford University have started first booster Ebola vaccine trials to test its safety and evaluate its potential to further increase the immune responses seen in healthy volunteers.
The second stage of the Ebola trial is conducted as part of an ongoing trial at Oxford University’s Jenner Institute.
All adult volunteers received an experimental Ebola vaccine that is under development by GSK and US National Institutes of Health (NIH).
Between 17 September and 18 November 2014, the Oxford University trial had 60 people vaccinated with initial results expected before Christmas.
The first GSK / NIH Ebola vaccine ‘prime’ uses a single Ebola virus gene in a chimpanzee adenovirus to generate an immune response.
Approximately 30 volunteers will now receive a second candidate Ebola vaccine ‘booster’ of a different type developed by Denmark-based Bavarian Nordic. This vaccine uses the same Ebola virus gene in a modified vaccinia Ankara (MVA) virus.
Jenner Institute professor Adrian Hill, who is leading the trial, said: "The aim of this trial is to tell us something about the safety of these two Ebola vaccines used in combination, and whether the second booster vaccine can increase immune responses further.
"We have seen promising results from the first 20 people vaccinated with a multi-strain formulation in the US, the vaccine is well tolerated and does generate an immune response.
"How long that response lasts, and what level of immune response we need to offer people protection from Ebola we don’t know as yet.
"It is only larger trials in West Africa that will begin to tell us that."
The latest trial will test the booster vaccine’s safety, given from three to ten weeks after the first and will measure immune responses seen in the volunteers over a period of six months.
An approach of using two vaccines helps to gather significant data about an initial immune response and the level of the body’s immune response.
The new Oxford trial will be funded under a grant from the Wellcome Trust, Medical Research Council (MRC) and the UK Department for International Development (DFID).
In response to the Ebola outbreak in West Africa, several safety trials of the GSK / NIH vaccine candidate were fast-tracked in the US, UK, Mali and Switzerland.
Image: A colourised transmission electron micrograph (TEM) revealed some of the ultrastructural morphology displayed by an Ebola virus virion. Photo: courtesy of CDC / Cynthia Goldsmith.