Effect of travel distance on household demand for typhoid vaccines: implications for planning.

Typhoid fever causes millions of illnesses and hundreds of thousands of deaths yearly. Vaccinations would mitigate this problem, but the users would probably have to pay some or most of the cost. Several willingness-to-pay studies have assessed the effect of price on private demand to provide a basis for financial planning of campaigns, but the effect of travel distance, which is a potentially important determinant of demand, has not been studied. This paper thus has two objectives: (i) conduct a willingness-to-pay survey to assess the effects of distance, price and other variables on the private demand for typhoid vaccinations in a rural township of China where a campaign is under consideration; and (ii) embed the demand function in a mathematical model to address three planning questions; should each village have its own clinic, would one clinic be best or should the number of clinics be something in-between? Private vaccine demand was found to depend on and be inelastic with respect to both price and travel distance. A 1-km increase in distance caused the number of vaccinations demanded to decrease the same as a $0.5 increase in price. Thus, the marginal rate of substitution was $0.5 per km. A single clinic would be best for the township only if diseconomies of scale in supplying vaccinations exceeded the marginal rate of substitution. Otherwise, multiple clinics close to users would be optimal. Thus, deciding the number, location and capacities of clinics for vaccination planning is as important as deciding what price(s) to charge.

An optimization model for reducing typhoid cases in developing countries without increasing public spending.

This article considers the investment case for using the Vi polysaccharide vaccine in developing countries from two perspectives: reducing typhoid cases and limiting new health care spending. A case study is presented using data from South and Southeast Asia. The purpose of the paper, however, is to draw broad implications that may apply to developing countries in general. Typical consumer demand functions developed from stated preference household surveys in South and Southeast Asia are used to predict probabilities of adults and children purchasing typhoid vaccinations at different prices. These functions are incorporated in a formal mathematical model. Using data from the recent literature for South and Southeast Asia for typhoid incidence, Vi vaccine effectiveness, public cost of illness, and vaccination program cost, three mass vaccination policy alternatives are evaluated: charging adults and children different (optimal) prices, charging uniform prices, and providing free vaccines. Assuming differential pricing is politically feasible, different vaccine prices for children and adults would maximize the number of typhoid cases avoided from a mass vaccination program if the public sector faces a budget constraint on spending for the vaccination program. However, equal prices for children and adults produce very similar results, and they might be more readily accepted by the community. Alternatively, if vaccines are free, the number of cases is not significantly reduced compared to either pricing policy, but a large external financial contribution from government or donors would be required. A Monte Carlo simulation explores the effects of uncertain parameters on vaccination program outcomes.