Scientists at Oxford University have kicked off a 30-patient trial assessing the efficacy of a candidate booster vaccine against Ebola.

All the adult volunteers have previously received an experimental Ebola vaccine being developed by GSK and the US National Institutes of Health (NIH) as part of an ongoing trial at the Jenner Institute at Oxford, initial results from which are expected before Christmas.

But the new part of this trial - which continues to be funded by a grant from the Wellcome Trust, the Medical Research Council and the UK Department for International Development - will see participants given a second candidate Ebola vaccine of a different type made by Danish group Bavarian Nordic. 

The study will test the safety of this booster vaccine, given three-10 weeks after the first, and will measure the immune responses seen in the volunteers over a six-month period. The aim is to shed some light on the safety of the two Ebola vaccines used in combination, and if the second booster further increases any immune response.

'If a single dose of an Ebola vaccine is sufficient, it makes absolute sense to use that. But it also makes sense at this early stage of trials to see if a second booster vaccine can greatly increase the levels of immune responses produced,” said Professor Adrian Hill, who is leading the trial at Oxford University's Jenner Institute, also noting that there is still “real uncertainty about what level of vaccine-induced immunity is required to protect people against Ebola”.