Containing Ebola at the Source with Ring Vaccination

​Stefano Merler, Marco Ajelli, Laura Fumanelli, Stefano Parlamento, Ana Pastore y Piontti, Natalie E. Dean, Giovanni Putoto, Dante Carraro, Ira M. Longini Jr., M. Elizabeth Halloran, Alessandro Vespignani
PLOS Neglected Tropical Diseases
10(11): e0005093 (2016)
November 2, 2016

Abstract

Interim results  from the Guinea Ebola ring vaccination trial suggest high efficacy of the  rVSV-ZEBOV vaccine. These findings open the door to the use of ring  vaccination strategies in which the contacts and contacts of contacts of each  index case are promptly vaccinated to contain future Ebola virus disease  outbreaks. To provide a numerical estimate of the effectiveness of ring  vaccination strategies we introduce a spatially explicit agent-based model to  simulate Ebola outbreaks in the Pujehun district, Sierra Leone, structurally  similar to previous modelling approaches. We find that ring vaccination can  successfully contain an outbreak for values of the effective reproduction  number up to 1.6. Through an extensive sensitivity analysis of parameters characterising  the readiness and capacity of the health care system, we identify  interventions that, alongside ring vaccination, could increase the likelihood  of containment. In particular, shortening the time from symptoms onset to  hospitalisation to 2–3 days on average through improved contact tracing  procedures, adding a 2km spatial component to the vaccination ring, and  decreasing human mobility by quarantining affected areas might contribute  increase our ability to contain outbreaks with effective reproduction number  up to 2.6. These results have implications for future control of Ebola and  other emerging infectious disease threats.