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

On August 1, 2018, the World Health Organization (WHO) announced a new outbreak of Ebola virus disease (EVD) in North Kivu Province, Democratic Republic of Congo (DRC) [1] . Epidemiological investigations traced EVD cases back to the week of April 30 and identified the initial epicenter to be Mabalako. This region of DRC (Fig 1) has over five million inhabitants, some of whom suffer from armed conflict, humanitarian crisis, and displacement to the bordering countries of Uganda and Rwanda [2] . Since the outbreak began, its magnitude has surpassed all other EVD outbreaks in DRC, becoming the second largest in history to date. As of February 25, 2019, 875 EVD cases had been reported (65 probable and 810 confirmed), and the Ministry of Health of DRC, the World Health Organization, and other organizations were responding to the Ebola outbreak [3] . This is the first EVD outbreak to occur in an armed conflict zone, and this new context has created challenges to the outbreak response [4] . Uptake of traditional control measures such as contact tracing and safe burials has varied with the community, even with the rapid deployment and widespread availability of experimental vaccines and therapeutics [3] . Our understanding of the impact of scientific advances on EVD transmission has been evolving; there has been an underlying, untested assumption that vaccination may reduce epidemic transmission [5] . Mathematical modeling of simulated EVD epidemics suggested that vaccination coverage as low as 40% in the general population and 95% in healthcare workers (HCWs) may avert another epidemic similar to size of the West African one [6] . Studies have yet to estimate the levels of vaccination coverage associated with epidemic decline. An even greater potential problem in difficult-to-access outbreak areas is ascertainment of vaccination coverage among contacts and contacts of contacts. Mathematical models are needed that can produce relatively accurate forecasts in the setting of such unknown but important outbreak response metrics.