The World Health Organization (WHO) is supporting the acceleration of new Ebola interventions in Africa, in particular the development of additional candidate vaccines. The Strategic Advisory Group of Experts (SAGE) on Immunization previously recommended that urgent consideration should be given to evaluating new candidate vaccines in randomised trials among health care and front line workers in high risk areas which are not directly related to a case of Ebola (ie, in areas the outbreak has not reached). As part of these efforts, WHO has been working with several partners to discuss study designs that could help assess the efficacy and effectiveness of available candidate vaccines.
In order to determine suitability of Ebola vaccines for clinical studies, WHO reviewed data generated by Ebola vaccine manufacturers on two candidate vaccines: the adenovirus 26 vectored glycoprotein / MVA-BN (Ad26.ZEBOV/ MVA-BN) vaccine developed by Johnson & Johnson, and the CanSino-Beijing Institute of Biotechnology (Ad5-EBOV) vaccine.
These vaccines were assessed according to a framework developed by the WHO Scientific and Technical Advisory Committee on Ebola Experimental interventions (STAC-EE) in 2015 and previously used to assess other candidate Ebola vaccines. The experts considered a number of criteria to be used in the selection of the vaccine that would be tested in clinical studies and observational studies. As recommended by SAGE in April 2019, proposed studies should be scientifically and epidemiologically justified, and have appropriate approvals including from all relevant African and other regulatory and ethics authorities. Criteria included acceptable safety profile, induction of appropriate immune responses, including neutralizing antibodies, and the timely availability of sufficient supplies of vaccine doses.
The assessment performed is not an endorsement of either vaccine, but is intended to guide stakeholders and national authorities in whose countries clinical trials may be proposed. The final decision whether and when to proceed with any clinical trials is the sole prerogative of national authorities.
