Evaluating large-scale blood transfusion therapy for the current Ebola epidemic in Liberia

Abstract

Background: To combat the 2014-2015 Ebola virus disease (EVD) epidemic in West Africa, the World Health Organization urged the rapid evaluation of convalescent whole blood (CWB) and plasma (CP) transfusion therapy. However, the feasibility and likely impacts of broad implementation of transfusions are yet unknown.

Methods: We extended an Ebola virus transmission model published by the Centers for Disease Control and Prevention to include hospital-based convalescent donations and transfusions. Using recent epidemiological estimates for EVD in Liberia and assuming that convalescent transfusions reduce the case-fatality rate to 12.5% (range, 7.5%-17.5%), we projected the impacts of a countrywide ramp-up of transfusion therapy.

Results: Under the 10% case-hospitalization rate estimated for Liberia in September 2014, large-scale CP therapy is expected to save 3586 lives by October 2015 (3.1% mortality reduction; 95% confidence interval [CI], .52%-4.5%). Under a higher 30% hospitalization rate, CP transfusions are expected to save 151 lives (0.9% of the total; 95% CI, .21%-11%).

Conclusions: Transfusion therapy for EVD is a low-cost measure that can potentially save many lives in West Africa but will not measurably influence the prevalence. Under all scenarios considered, CP transfusions are predicted to achieve greater reductions in mortality than CWB.

Keywords: Ebola virus disease; convalescent blood; dynamic model; polyclonal antibody therapy; transfusion.

Figure 1.

Projected impact of large-scale transfusion therapy in Liberia, beginning 1 December 2014, on cumulative fatalities. The gray ribbon denotes the 95% confidence interval (CI) for expected fatalities, assuming no transfusion intervention. The arrow denotes the start of the transfusion intervention. Under a 10% hospitalization rate, convalescent plasma (CP) transfusions are expected to reduce cumulative fatalities by 3.1% (95% CI, .52%–4.5%) by 1 October 2015. Increasing the hospitalization rate to 30% by 1 December 2014 is projected to contain the spread; in this case, CP transfusion is expected to achieve a 0.9% reduction in cumulative fatalities (95% CI, .21%–11%). Given the more limited supply of convalescent whole blood (CWB) transfusions, they are projected to lower expected cumulative fatalities by only 0.73% (95% CI, .19%–1.1%) and 0.37% (95% CI, .069%–2.6%) under 10% and 30% hospitalization rates, respectively.

Figure 2.

Projected numbers of patients with Ebola virus disease who are not hospitalized, are hospitalized without transfusion therapy, and are hospitalized with transfusion therapy, assuming a 10% hospitalization rate in Liberia, using convalescent-whole blood (CWB) transfusions (A), and convalescent plasma (CP) transfusions (B). Even if equipment and staff are available, it would not be possible to treat all hospitalized patients, owing to shortages of convalescent donors. With a CWB-based intervention, we estimate that 14% of patients hospitalized after the December 2014 implementation would receive therapy; with CP, the estimated fraction treated increases to 60%.