Economic evaluation using dynamic transition modeling of ebola virus vaccination in lower-and-middle-income countries
With the increasing occurrence of infectious diseases in lower-and-middle-income countries (LMICs), emergency preparedness is essential for rapid response and mitigation. Economic evaluations of mitigation technologies and strategies have been recommended for inclusion in emergency preparedness plans. We aimed to perform an economic evaluation using dynamic transition modeling of ebola virus disease (EVD) vaccination in a hypothetical community of 1,000 persons in the Democratic Republic of Congo (DRC).
Using a modified SEIR (Susceptible, Exposed, Infectious, Recovered, with Death added [SEIR-D]) model that accounted for death and epidemiological data from an EVD outbreak in the DRC, we modeled the transmission of EVD in a hypothetical population of 1,000. With our model, we estimated the cost-effectiveness of an EVD vaccine and an EVD vaccination intervention.
The results showed vaccinating 50% of the population at risk prevented 670 cases, 538 deaths, and 22,022 disability-adjusted life years (DALYs). The vaccine was found to be cost-effective with an incremental cost-effectiveness ratio (ICER) of $95.63 per DALY averted. We also determined the minimum required vaccination coverage for cost-effectiveness to be 40%. Sensitivity analysis showed our model to be fairly robust, assuring relatively consistent results even with variations in such input parameters as cost of screening, as well as transmission, infection, incubation, and case fatality rates.
EVD vaccination in our hypothetical population was found to be cost-effective from the payer perspective. Our model presents an efficient and reliable approach for conducting economic evaluations of infectious disease interventions as part of an emergency preparedness plan.
Infectious diseases affect lower-and-middle-income (LMIC) countries, with their limited resources, disproportionately more. This is certainly the case for ebola virus disease (EVD), a rare, severe, and mostly fatal disease. Vaccination is now available, but whether it is cost-effective remains an open question. We evaluated its cost-effectiveness by modeling the spread of EVD in a hypothetical population of 1000 persons. Using data from an EVD outbreak in the Democratic Republic of Congo (DRC), we estimated how many of persons susceptible to infection were exposed to the virus, became infected, recovered, or died. We did so for two scenarios: vaccinating versus not vaccinating enough people to achieve herd immunity. We assumed vaccinating 50% of the people and estimated how many infections, deaths, and disability-adjusted life years (DALY; the loss of the equivalent of a year of full health) would be prevented by vaccination. Our cost-effectiveness metric was the incremental cost of preventing one DALY.
The outcomes of vaccination offset the additional costs. Vaccinating 50% of the population of 1000 cost an additional $2,081,358 but prevented 670 infections, 538 deaths, and 22022 DALYs. Preventing one DALY cost $95.63. This is very cost-effective as it is less than the gross domestic product (GDP) per capita for the DRC of $556.81. Vaccination below 40% of the population was less cost-effective, was most cost-effective at the herd immunity threshold of 45.3%, beyond which there were diminishing returns. Summarized, vaccination against EVD is clinically very effective and certainly worth the additional cost.
