An SEIR Model of Potential Vaccination Program in the 2014 Sierra Leone Ebola Epidemic

Document Type


Publication Date



The March 2014 Ebola outbreak in Sierra Leone and Liberia has significantly strained public health systems in both countries. Current epidemic models focus on non-vaccine treatment interventions. We modeled the potential consequences of future vaccine deployment in Sierra Leone, specifically the relationship between vaccination rates, date of commencement of a vaccination program, vaccine efficacy, and epidemic size. As a baseline model of the epidemic in the absence of control measures, we utilized a version of the SEIR (susceptible-exposed-infectious-recovered) epidemic model utilized by Chowell et al. to model Ebola outbreaks in the Congo parameterized using September 2014 estimates from the WHO. We utilized a model developed by Althaus using October 2014 epidemic data as a baseline for epidemic sizes in the presence of non-vaccination interventions. We plan to investigate whether the deployment of a moderately effective vaccine at a high vaccination rate can yield a similar reduction in deaths as a highly effective vaccine at a smaller vaccination rate.

Preliminary data utilizing the WHO baseline model, assuming the start of a vaccination program concurrent with the start of the epidemic in Sierra Leone, found that at a vaccine efficacy of 30%, a vaccination rate of 1000 individuals per day results in a 64% reduction of cases by November 2014. Data modeled using vaccination rates ranging from 1000 individual per day to 8000 individuals per day, vaccine efficacy values ranging from 30% to 70% efficacy, and various vaccination program commencement dates will be presented.


Modeling the Spread of Ebola in West Africa Workshop


Atlanta, GA