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Research areas
Objectives: Assess the effectiveness of ring vaccination in controlling an Ebola virus outbreak in theDemocratic Republic of Congo.Methods: This analysis focuses on two areas of the Democratic Republic of Congo, Beni andButembo/Katwa, which were affected during the 2018-2020 Ebola outbreak. To simulate Ebola virustransmission, we used a spatially explicit agent-based model with households, health care facilities, andEbola treatment units. Model parameters were calibrated using data collected under the ring-vaccinationexpanded-access protocol implemented during the outbreak. The model was used to estimate the impactof the deployed ring vaccination strategy, compared to what would have happened if there had been noring vaccination. The impact of alternative vaccination strategies (mass vaccination, targeted geographicvaccination, and ring-plus) was evaluated as well.Results: Compared to a hypothetical scenario where vaccination was not implemented, ring vaccinationwas estimated to have averted 54.3% (SD, 32.5%) and 62.7% (SD, 23.2%) of potential cases in Beni andButembo/Katwa, respectively. Under ring vaccination, the average number of averted cases per 1000 vaccine doses administered was 15.1 (SD, 16.8) and 27.8 (SD, 22.9), in Beni and Butembo/Katwa, respectively.In terms of number of averted cases per vaccine dose, ring vaccination was estimated to be more efficientthan any of the other evaluated vaccination strategies.Conclusion: Despite some level of social instability, ring vaccination with the rVSV-ZEBOV vaccine washighly effective during the 2018-2020 Ebola outbreak in the Democratic Republic of Congo. As comparedto alternative vaccination strategies, ring vaccination was estimated to be the most efficient.
