Cost-effectiveness of dog rabies vaccination programs in East Africa

Abstract

Background: Dog rabies annually causes 24,000-70,000 deaths globally. We built a spreadsheet tool, RabiesEcon, to aid public health officials to estimate the cost-effectiveness of dog rabies vaccination programs in East Africa.

Methods: RabiesEcon uses a mathematical model of dog-dog and dog-human rabies transmission to estimate dog rabies cases averted, the cost per human rabies death averted and cost per year of life gained (YLG) due to dog vaccination programs (US 2015 dollars). We used an East African human population of 1 million (approximately 2/3 living in urban setting, 1/3 rural). We considered, using data from the literature, three vaccination options; no vaccination, annual vaccination of 50% of dogs and 20% of dogs vaccinated semi-annually. We assessed 2 transmission scenarios: low (1.2 dogs infected per infectious dog) and high (1.7 dogs infected). We also examined the impact of annually vaccinating 70% of all dogs (World Health Organization recommendation for dog rabies elimination).

Results: Without dog vaccination, over 10 years there would a total of be approximately 44,000-65,000 rabid dogs and 2,100-2,900 human deaths. Annually vaccinating 50% of dogs results in 10-year reductions of 97% and 75% in rabid dogs (low and high transmissions scenarios, respectively), approximately 2,000-1,600 human deaths averted, and an undiscounted cost-effectiveness of $451-$385 per life saved. Semi-annual vaccination of 20% of dogs results in in 10-year reductions of 94% and 78% in rabid dogs, and approximately 2,000-1,900 human deaths averted, and cost $404-$305 per life saved. In the low transmission scenario, vaccinating either 50% or 70% of dogs eliminated dog rabies. Results were most sensitive to dog birth rate and the initial rate of dog-to-dog transmission (Ro).

Conclusions: Dog rabies vaccination programs can control, and potentially eliminate, dog rabies. The frequency and coverage of vaccination programs, along with the level of dog rabies transmission, can affect the cost-effectiveness of such programs. RabiesEcon can aid both the planning and assessment of dog rabies vaccination programs.

Fig 1

Cases of dog rabies for alternative dog rabies vaccination programs in East Africa: A. Low levels of transmission; B. High levels of transmission^a Footnotes: a. Results for two scenarios for dog rabies vaccination programs in an East African population of 1 million persons (approximately 2/3 urban, 1/3 rural), with approximately 82,000 dogs (Table 1). Vaccination programs: Option 1, annual mass dog vaccination, resulting in 50% of the dog population vaccinated, and Option 2, biannual (twice per year) mass dog vaccination, resulting in 20% of the dog population vaccinated for each vaccination program. Rabies transmission risk is defined, in part, by the number of bites per rabid dog to another dog (see Table 2).

Fig 2

Cases of human rabies per million human population for alternative dog rabies vaccination programs in East Africa: A. Low levels of transmission; B. High levels of transmission^a Footnotes: a. Results for two scenarios for dog rabies vaccination programs in an East African population of 1 million persons (approximately 2/3 urban, 1/3 rural), with approximately 82,000 dogs (Table 1). Vaccination programs: Option 1, annual mass dog vaccination, resulting in 50% of the dog population vaccinated, and Option 2, biannual (twice per year) mass dog vaccination, resulting in 20% of the dog population vaccinated for each vaccination program. Rabies transmission risk is defined, in part, by the number of bites per rabid dog to another dog (see Table 2).

Fig 3

Sensitivity analysis: Estimated number of dog rabies cases for different proportions of male dogs neutered^a Footnotes: a. Results estimated assuming an East African population of 1 million persons (approximately 2/3 urban, 1.3 rural), with approximately 82,000 dogs (Table 1), use of vaccination Option 1 (50% of dogs are vaccinated against rabies each year), and assuming the high dog-dog rabies transmission scenario (see Table 2).

Fig 4

Sensitivity analysis: Cases of dog rabies for alternative annual dog rabies vaccination programs in East Africa: A. Low levels of transmission; B. High levels of transmission^a Footnotes: a. Results for dog rabies vaccination programs in an East African population of 1 million persons (approximately 2/3 urban, 1/3 rural), with approximately 82,000 dogs (Table 1). Rabies transmission risk is defined, in part, by the number of bites per rabid dog to another dog (see Table 2).

Fig 5. Sensitivity analyses: Impact in number of rabid dogs with changes in dog vaccination coverage, dog birth rate and life expectancy, and initial dog-to-dog rabies transmission.

^a Footnotes: a: Analyses run assuming 7.5% of dogs are neutered (Table 3), and using values for urban scenario (Table 1). Baseline values for the variables altered here are: Vaccination coverage 50%; Annual dog birth rate 676/1,000 dogs, dog life expectancy 3.0 years, and an Ro of 1.2.