Providing Additional Information on the Safety and Effectiveness of an Ebola Vaccine

Ebola Virus Disease remains ill-known by populations, creating fear and mistrust, is highly contagious, requiring strict isolation measures and with only supportive therapy available that has limited impact on case-fatality which remains high (30 -80%).1 Among vaccines in development, the rVSVΔG-ZEBOV-GP vaccine has given the most promising results in terms of efficacy and safety having been evaluated now in more than 10,000 individuals.

Ring vaccination is a known strategy to control epidemics with specific transmission chains and has been successfully implemented to eradicate smallpox. Ring vaccination enhances standard public health measures of contact tracing, isolation, and community engagement and could be effective when such measures are in place. Building on the interim results of the Ebola ça Suffit trial, there is a need for continued access to a vaccine of which available results suggest that it is safe and likely efficacious against EVD. Although only isolated cases have been reported in Guinea, Sierra Leone and Liberia in 2016, 10 the risk of resurgence or of continued isolated cases in West Africa remains. Moreover, a new outbreak with Ebola Zaïre could start any moment in any of the countries where previous outbreaks occurred as in for example Democratic Republic of Congo and Uganda.

However, the unusual design of the ring trial and the decision to abandon the control group because of strong evidence that the vaccine prevented disease means there may not be enough data to ensure approval from regulatory agencies. Therefore, additional information is still required to consolidate knowledge on the rVSVΔG-ZEBOV-GP vaccine to support regulatory approval and licensure for future access. Additional information is also needed on ring vaccination and contextual adaptations to this approach to ensure its feasibility and effectiveness in the control of Ebola outbreaks in potentially diverse contexts.