Projections of epidemic transmission and estimation of vaccination impact during an ongoing Ebola virus disease outbreak in Northeastern Democratic Republic of Congo, as of Feb. 25, 2019

Worden, Lee; Wannier, Rae; Hoff, Nicole A.; Musene, Kamy; Selo, Bernice; Mossoko, Mathias; Okitolonda-Wemakoy, Emile; Muyembe Tamfum, Jean Jacques; Rutherford, George W.; Lietman, Thomas M.; Rimoin, Anne W.; Porco, Travis C.; Kelly, J. Daniel

Another outbreak response challenge has been ascertaining the level of vaccination coverage that has occurred during the ring vaccination program. For the ring vaccination program to be theoretically effective at reducing transmission, an uncertain proportion of contacts and contacts of contacts need to receive the vaccine [6] . We estimated that transmission rates are higher than would be expected under target levels of 62% coverage due to contact tracing and vaccination. Under our stochastic model's assumptions, the elevated transmission rates, relative to those of past outbreaks, needed to reproduce this outbreak's epidemic trajectory are highly unlikely to be randomly observed with high vaccination coverage. This model estimate may serve as a loose proxy for the outbreak response challenges. Thus, outbreak response teams may need to consider other control and care strategies to end the outbreak. Under current circumstances, mass vaccination in regions of high prevalence or areas where the outbreak has newly arrived may be a more effective strategy to reduce EBOV transmission than ring vaccination. Aggressive supportive care, experimental therapeutics and high-quality facilities (e.g. air-conditioned, individualized) have also been described as part of the outbreak response. These interventions have the potential to improve health-seeking behaviors and possibly reduce EBOV transmission in communities that are resistant to control efforts [15] , but further studies are needed.