[An empirical research for demand of influenza vaccination]

This article examines the demand for influenza vaccination in Japan.

Original date were obtained from a survey conducted by the authors. Two approaches, usual demand analysis and conjoint analysis, were employed. The second approach, conjoint analysis, uses people's statements on how they would respond to different hypothetical situations. In this research, we ask people whether they wish to be vaccinated given different circumstances such as costs of vaccination, degree of convenience, and outbreak news.

In the demand analysis, the vaccination rate during the 1999-2000 season was found to have increased by 0.8 percentage points compared to that of the previous season. The rate increased by 1.0 to 3.5 percentage points among the group of people who experienced influenza in the previous season. The vaccination rate also increased by 31-47 percentage points for those who were vaccinated in the previous season. A 10 percentage increase in household income decreased the demand for vaccination by 2 percentage points. Although household income was significant in only with the largest sample, this result may indicate that the time or opportunity cost for vaccination decreases the vaccination demand. In the conjoint analysis, the financial cost was significantly negative. When the cost was reduced from the current level of 6,000 yen to free of charge, the vaccination rate would increase by 43.5 percentage points. Were vaccination available at night or during holidays,! or at school or work, the rate would increase by 11 percentage points, or 16 percentage points, respectively. Most of all, news of influenza prevalence was very influential in increasing the desire for vaccination by 33 percentage points. Vaccination experience and last year's influenza experience were both significantly positive, increasing the rate by 22 and 8 percentage points, respectively.

In the demand analysis, influenza experience and history of vaccination during the 1999-2000 season were found to be influential regarding the decision for vaccination. From the conjoint analysis, providing vaccination of night or during holidays, as well as at work or at schools would increase the demand. News of influenza outbreaks were also found to increase the vaccination demand. Higher income, however, was found to have a negative influence, suggesting that opportunity costs may be an important factor for some individuals. Habit formation effects through a history of vaccination plays quite an important role in vaccination demand.