Health Policy and Planning Advance Access originally published online on January 30, 2008
Health Policy and Planning 2008 23(2):125-136; doi:10.1093/heapol/czm047
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Comparison of cost-of-illness with willingness-to-pay estimates to avoid shigellosis: evidence from China
1 University of North Carolina at Chapel Hill, USA.
2 Fudan University, Shanghai, China.
3 Research Triangle Institute, Durham, NC, USA.
4 International Vaccine Institute, Seoul, Korea.
5 Centers of Disease Control, Zhengding County, Hebei Province, China.
6 University of North Carolina at Chapel Hill and Manchester Business School, USA.
* Corresponding author. Research Triangle Institute, Health, Social and Economics Research, 3040 Cornwallis Road, Research Triangle Park, NC 27709, USA. Tel: +1–919–541–7130. Fax: +1–919–541–6683. E-mail: cpoulos{at}rti.org
Previous studies have shown that cost of illness (COI) measures are lower than the conceptually correct willingness-to-pay (WTP) measure of the economic benefits of disease prevention. We compare COI with stated preference estimates of WTP associated with shigellosis in a rural area of China. COI data were collected through face-to-face interviews at 7 and 14 days after culture-confirmed diagnosis. WTP to avoid an episode similar to the one the respondent just experienced was elicited using a sliding-scale payment card. In contrast to previous studies’ findings, average COI estimates (2002 PPP adjusted US$28.2) approximate an upper bound estimate of WTP, rather than a lower bound. One explanation for the similarity between COI and WTP is that preventive expenditures and disutility due to pain and suffering are low for shigellosis. WTP to avoid additional cases in children aged 0–5 years is higher than in adults. Also, average COI (2002 PPP adjusted US$28.4) for children is similar to a lower bound estimate of WTP (2002 PPP adjusted US$16.4) and lies within the WTP range. Because the monetary loss associated with another episode in children is small, caregivers’ higher WTP may be attributable to the disutility of illness due to the children's pain and suffering. These findings suggest that for some diseases, COI may approximate more comprehensive measures of economic benefits.
Key Words: Cost of illness, willingness to pay, WTP, shigellosis, China
Accepted for publication 19 November 2007.