Valuation of symptomatic hepatitis A in adults - Estimates based on time trade-off and willingness-to-pay measurement

Background: The cost effectiveness of hepatitis A prevention is typically assessed by comparing vaccination costs with the number of life-years saved. This endpoint does not consider the benefits of preventing nonfatal yet symptomatic infections. Nearly as many days of healthy life are lost to hepatitis A morbidity as mortality. Objective: To investigate the value American adults place on preventing hepatitis A symptoms by using the willingness-to-pay and time trade-off metrics. Methods: We provided a written description of hepatitis A symptoms to 181 American adults, who judged the amounts of money and lifespan they would forego to avoid them. The description made no reference to the possibility of fatality, and respondents were asked not to consider costs of medical care and work loss. We investigated relationships between demographic characteristics and each metric, the relationship between the two metrics, and the test/re-test reliability of the metrics. Results: Respondents would pay a median of $US2000 (inter-quartile range, $US500 to 5000; 2001 values) for risk-free prevention of hepatitis A symptoms. Alternatively, they would forego a median of 28 days survival (inter-quartile range, 6 to 40 days) for cost-free prevention. There was modest correlation between willingness-to-pay and time trade-off responses (r=0.24, p<0.01), suggesting these metrics measure independent aspects of preference. Strong correlations between measures obtained 30 days apart support the test/re-test reliability of willingness to pay (r=0.70, p<0.01) and time trade-off (r=0.73, p<0.01) metrics. In multivariate analyses, higher household income (p=0.02) predicted greater willingness to pay in dollars. Male gender (p<0.01) predicted greater willingness to forego life expectancy for better health. Conclusion: In our study population of US adults, most were willing to pay or trade life expectancy for a hypothetical preventative drug for hepatitis A symptoms. The amount respondents were willing to pay appears dependent on their income level while males are willing to trade more life expectancy than female respondents. The values expressed should be considered in assessments of hepatitis A prevention.