Cost of childhood diarrhoea in rural South Africa: exploring cost-effectiveness of universal zinc supplementation.

Objective: To describe the cost of diarrhoeal illness in children aged 6-24 months in a rural South African community and to determine the threshold prevalence of stunting at which universal Zn plus vitamin A supplementation (VAZ) would be more cost-effective than vitamin A alone (VA) in preventing diarrhoea. Design: We conducted a cost analysis using primary and secondary data sources. Using simulations we examined incremental costs of VAZ relative to VA while varying stunting prevalence. Setting: Data on efficacy and societal costs were largely from a South African trial. Secondary data were from local and international published sources. Subjects: The trial included children aged 6-24 months. The secondary data sources were a South African health economics survey and the WHO-CHOICE (CHOosing Interventions that are Cost Effective) database. Results: In the trial, stunted children supplemented with VAZ had 2.04 episodes (95% CI 1.37, 3.05) of diarrhoea per child-year compared with 3.92 episodes (95% CI 3.02, 5.09) in the VA arm. Average cost of illness was $Int 7.80 per episode (10th, 90th centile: $Int 0.28, $Int 15.63), assuming a minimum standard of care (oral rehydration and 14 d of therapeutic Zn). In simulation scenarios universal VAZ had low incremental costs or became cost-saving relative to VA when the prevalence of stunting was close to 20 %. Incremental cost-effectiveness ratios were sensitive to the cost of intervention and coverage levels. Conclusions: This simulation suggests that universal VAZ would be cost-effective at current levels of stunting in parts of South Africa. This requires further validation under actual programmatic conditions.