Given the urgent need for a preventive Ebola vaccine strategy in the context of the Ebola epidemic, the clinical development plan followed an expedited scheme, that aimed to start a Phase 2B large scale safety and immunogenicity study as soon as possible while assuring the safety of the trial participants. The study has been performed from 2015 until 2019.

Phase 1 trials to assess the safety and immunogenicity data of the candidate heterologous 2-dose vaccination regimen in healthy volunteers were performed in the UK, the US, Kenya, Uganda and Tanzania. Both heterologous 2-dose vaccination regimen (Ad26.ZEBOV dose 1 + MVA-BN-Filo booster dose; and MVA-BN-Filo dose 1 + Ad26.ZEBOV booster dose) administered at different intervals were tested in these trials.

Phase 2 trials of EBOVAC2 started as soon as the post-prime safety and immunogenicity data from the UK Phase I were available. Phase 2 trials were conducted in healthy volunteers in Europe (France and UK) and non-epidemic African countries (to be determined). HIV positive adults were also vaccinated in African countries. The rationale for inclusion of European volunteers in Phase 2, in addition to the trials in Africa, was to allow for higher sensitivity in safety signal detection in populations with low incidence of febrile illnesses, to generate negative control specimens for assay development, to allow for inclusion of health care workers or military personnel that may be deployed to Ebola-endemic regions.