A policy to promote influenza vaccination: A behavioral economic approach

Abstract

The aims of this study were to identify the predictors of people's willingness to be vaccinated against influenza and to determine how to improve the inoculation rate. The study was based upon the results of our original large-scale survey conducted in the USA in 2005. A model of bounded rationality can explain vaccination behavior fairly well: (a) people evaluate the costs and benefits of vaccination by applying risk aversion and time preference; (b) the ‘status quo bias’ of those who were vaccinated in the past affects their decision to be vaccinated in the future; and (c) overconfidence indirectly affects the decision through the moderation of perceived variables. Policy implications include: (a) dissemination of information about the vaccine is especially important among people who are inexperienced with the vaccine since they undervalue the effectiveness of vaccination; (b) lowering the total cost of vaccination, including time costs (for example, by offering the vaccine at workplaces) may raise the inoculation rate, especially among those inexperienced with the vaccine, since those who have experience with the vaccine tend to take it on a regular basis.

Introduction

Influenza vaccination has been shown to be cost effective in reducing morbidity and mortality in the older adult population, and in reducing morbidity, work absenteeism and use of healthcare resources among the healthy working adult population [1], [2], [3]. Vaccine prevents influenza in approximately 70–90% of healthy adults under the age of 65 and in 58% among persons over 60 years of age [1], [4]. Although influenza vaccination levels increased substantially during the 1990s, further improvements in vaccination coverage levels are needed. For example, in 2004 estimated rates of vaccination coverage among adults with high-risk conditions between the ages of 18 and 49 and among those between the ages of 50–64 were 26% and 46% respectively, substantially lower than the objectives of 60% set by Healthy People 2000 and Healthy People 2010 [5].

Theoretically, the socially optimal rate of inoculation should be substantially higher than the optimal rate for an individual, because contracting an infectious disease has far-reaching implications for society. Thus, increasing willingness to be inoculated is socially desirable, even if it does not conform to an individual's rational decision. In this paper, we investigate whether or not propagation of information regarding influenza and its vaccine will raise willingness to undergo inoculation.¹ This is not known a priori; it could be that more information will diminish people's willingness because they may unreasonably fear influenza and/or irrationally overestimate the effectiveness of flu inoculation. Of course, the opposite might be the case—that increased information will substantially promote inoculation. This paper attempts to identify what kind of information might be effective in raising the inoculation rate. In this sense, our study follows a behavioral economic approach and focuses on the bounded rationality of individuals. In addition to the effect of knowledge, we expected to find other behavioral factors, such as status quo bias and overconfidence effect, to affect the inoculation decision. Status quo bias refers to the situation in which people tend not to change an established behavior unless the incentive to change is compelling [7]. It was found that past experience with influenza vaccination is a predictor for willingness to be vaccinated [8], since those who were vaccinated previously may continue to do so annually as a matter of routine (maintaining the ‘status quo’). Another study included a multi-variant analysis that revealed previous influenza vaccination to be the single strongest predictor of subsequent vaccination behavior [9]. The overconfidence effect is the tendency of people to underestimate “real” objective risks [10].

To be useful in policy planning, analyses should consider comprehensive factors as well as irrational aspects of human beings. First, bounded rationality means that people are fairly rational and can be expected to make a decision on inoculation based on its benefits and costs. In particular, it is hypothesized that beliefs regarding the probability of contracting the flu, the severity of the illness and the effectiveness and side effects of the vaccine as well as preferences involving time and risks play important roles in assessing the costs and benefits of influenza inoculation. In addition, attributes such as gender and age may explain willingness to be vaccinated. The present study analyzes comprehensive factors regarding people's willingness to be vaccinated against the flu. The analysis has been made possible because of our original large survey conducted across the USA.

It is natural to suppose that people agree to be vaccinated based on perceived costs and benefits, which, in turn, depend on subjective beliefs regarding influenza and vaccination. Indeed, the Health Belief Model (HBM) explains and predicts preventive health behavior in terms of belief patterns that focus on the relationship between health behaviors and utilization of health services [11]. According to the HBM, willingness to be vaccinated against influenza depends on the following predictors: perceived susceptibility to influenza, beliefs about the severity of influenza, perceived benefits of the vaccine in preventing influenza, perceived barriers to being vaccinated, impact of cues (such as media information or physician recommendation) to action and degree of motivation for other health behaviors [12]. Indeed, cited reasons for not getting vaccinated against influenza were similar across studies with reference to perceived barriers, i.e., concern about side effects or vaccine safety, lack of effectiveness of the vaccine in preventing illness and lack of awareness [13], [14]. The HBM has been used to explore a variety of health behaviors, including vaccination [12], [13], [14], [15], [16]. Our study, likewise, is partially based on the HBM, and uses perceived variables elicited by a large-scale survey rather than actual values. As demonstrated in [17], a pure objective economic model does not predict the low rates of vaccination against influenza in the population, while a behavioral economic approach may explain these low vaccination rates by including subjective factors in the model. Their results show that lower subjective variables, such as subjective infection probability, effectiveness probability of vaccination and perceived severity of illness, as well as higher subjective variables, such as perceived costs of vaccination, may predict lower incentive to be vaccinated.

The paper is organized as follows. In Section 2, we explain our model and methods, Section 3 explains our survey, and Section 4 is devoted to the results. Section 5 summarizes and concludes the study.