A two-part Ebola vaccine regimen has been found to offer protection against the deadly disease for about a year in an early human trial.

The vaccine regimen induced an immune response that persisted for approximately one year in healthy adult volunteers, according to results from the phase-1 clinical trial published in the Journal of the American Medical Association. The experimental vaccines included Ad26.ZEBOV, developed by Johnson & Johnson, and MVA-BN-Filo, developed by Denmark-based Bavarian Nordic. 

Both of the vaccines in the regimen use harmless viral vectors, or carriers, to deliver proteins of the Ebola virus, which prompt an immune response. The trial, conducted by Matthew D. Snape of the University of Oxford and colleagues, enrolled healthy participants aged 18-50 years in Britain.

Participants were selected randomly to receive either the two-vaccine regimen or placebo (saltwater injections). Previously reported initial results showed the two-vaccine regimen is safe, well-tolerated and induced immune responses in participants eight months after immunisation.

Of the 75 participants who received the vaccine regimen, 64 remained in the study for a follow-up visit on day 360. No serious vaccine-associated adverse events were observed, and all 64 participants maintained antibodies to Ebola virus at day 360. The researchers noted that additional research is necessary to assess the durability of immunity beyond one year and the immune response to booster doses of vaccine.