20. Vaccine–Preventable Diseases

Cost-Effectiveness of Increasing Immunization Coverage for the Traditional EPI

WHO (2004) estimates that in 2001, 30 million children were inadequately immunized with DTP. Achieving higher coverage rates by improving access for remote populations, accelerating immunization delivery strategies, and introducing new vaccines will mean increasing the level of investment (Batt, Fox-Rushby, and Castillo-Riquelme 2004).

We estimated the costs of scaling up EPI coverage for a hypothetical population of 1 million in each region between 2002 and 2011. Costs were reported in 2001 dollars, and a 3 percent discount rate was applied. Brenzel (2005) provides details on the methods. The costs of scaling up coverage are based on vaccine and delivery costs per dose. We derived vaccine costs from the unit price of each vaccine (provided by WHO, UNICEF, and the Vaccine Fund); wastage rates for vaccines and injection supplies by strategy; the required injection supplies; and the number of doses per FIC. A 2 percent adjustment was made for inflation. We used data on the cost per FIC generated earlier to derive delivery costs per dose by strategy and region by subtracting the costs of vaccines, injection supplies, and fixed costs.

Fixed costs were excluded from the scaling-up exercise because they were assumed to remain constant during the projection period.

• First, the largest projected coverage increase of 9 percentage points (figure 20.1) may not require additional infrastructure investments.
  [Figure 20.1]
  

• Second, how and to what extent fixed costs would change by region is uncertain, and a conservative approach would be to exclude them.

• Third, because most immunization costs are recurrent costs, the analysis focuses on these.

• Finally, because the scale factor is derived from the unit costs of a health center visit, the assumption of constant fixed costs in the short run appears reasonable.

Previous studies have found that the main cost drivers of immunization costs are the mix of strategies and the scale of immunization programs (Brenzel and Claquin 1994; Dominguez-Uga 1988; Robertson and others 1992; Soucat and others 1997). Countries are unlikely to achieve 90 percent or more coverage relying on fixed facilities alone because of limited population access. We estimate the proportion of FICs obtained for each strategy by region.⁵ The best mix of strategies for increasing coverage will vary by country depending on the dispersion of the population, the access to health facilities, the vaccines being delivered, and the effectiveness of various strategies in reaching target populations. Estimates are also adjusted for the level of scale by a factor derived from the unit cost per health center contact by coverage level (Mulligan and others 2003), and details are provided in Brenzel (2005).

The total additional cost of reaching higher coverage levels was divided by the number of deaths averted. Coverage projections for 2002-11 were based on statistical modeling of official WHO and UNICEF estimates for the period between 1995 and 2002 for all developing countries. The model relates coverage in future years to that in the previous year, with the relationship between past and future coverage differing for each region and economic status combination.

Figure 20.1 shows historical and projected coverage rates by region. The figure shows that coverage increased in all the regions during the late 1980s under universal childhood immunization. After 1990, when funding for universal childhood immunization waned, the figure indicates the subsequent stagnation and, in some cases, the declines in coverage rates. For the scaling-up period, we project that the coverage of FICs will increase from 78 to 79 percent in East Asia and the Pacific, from 92 to 95 percent in Europe and Central Asia, from 88 to 90 percent in Latin America and the Caribbean, from 91 to 95 percent in the Middle East and North Africa, from 70 to 79 percent in South Asia, and from 52 to 61 percent in Sub-Saharan Africa. The projections show that three of the six regions are expected to achieve 90 percent FIC by 2011. East Asia and the Pacific, South Asia, and Sub-Saharan Africa will require additional intensive efforts to achieve higher coverage rates.

Table 20.6 reports the results of the scaling-up analysis for the traditional EPI vaccines, for tetanus toxoid vaccination for women of reproductive age, and for selected new vaccines. The discounted incremental cost per child vaccinated with the traditional EPI vaccines ranges from US$10.89 in Latin America and the Caribbean to US$12.84 in the Middle East and North Africa. The number of discounted deaths averted because of full immunization depends on incremental coverage rates and varies from 747 in Europe and Central Asia to 14,584 in Sub-Saharan Africa, resulting in regional variations in the discounted incremental cost per death averted from US$169 in Sub-Saharan Africa to US$1,754 in Europe and Central Asia.⁶

DALYs were estimated indirectly based on the ratio of deaths to DALYs for each disease in 2001. This ratio is applied to the hypothetical population in each World Bank region over the projection period. Calculated this way, the number of DALYs averted will not account for changes in the average age of infection that ordinarily results from expanding immunization coverage. This method over-estimates the number of DALYs and thus under-estimates the cost/DALY. Cost-effectiveness ratios should be treated as indicative only. The cost/DALY ranges from $2 to $20 for scaling up traditional immunizations.

For tetanus toxoid immunization, the additional discounted cost per person vaccinated ranges from US$3.28 to US$4.06. The cost per death averted varies from US$271 to more than US$190,000. The results of this analysis fall within the range of estimates reported in the literature (Berman and others 1991; Steinglass, Brenzel, and Percy 1993). Differences in coverage levels and in protection against neonatal tetanus through skilled delivery contribute to the variation in results across regions.

The analysis shows both an increase in costs and potential benefits from scaling up immunization programs. In practice, the costs and benefits related to scaling up in any one region will be highly dependent on a few countries or subnational areas within countries. Aggregate country- or region-level data do not reveal the efficiency that could best be obtained by targeting immunization efforts on specific countries or geographic areas rather than making diffuse investments across regions. For instance, Miller and others (1998) show that India and Nigeria contribute the most to estimates of global measles deaths; therefore, reducing transmission in those countries would contribute the most to reducing the global disease burden caused by measles.

Despite its importance for policy, empirical and country-specific evidence on how immunization program costs change as coverage increases is lacking. Because scaling up immunization coverage will require more intensive efforts to find unvaccinated children, an extra cost for vaccinating each additional child is generally expected. Nevertheless, most cost-effectiveness studies assume constant returns to scale (Elbasha and Messonnier 2004; Karlsson and Johannesson 1998) even when emerging evidence suggests that the cost of vaccinating each additional child may rise with the size of delivery unit (Valdmanis, Walker, and Fox-Rushby 2003). Box 20.1, which focuses on scaling up traditional immunization coverage, and box 20.2, which focuses on new antigens, summarize the results of two studies that shed more light on this subject.