Evolution of preferences for COVID-19 vaccine throughout the pandemic - The choice experiment approach.

In this study, we employ a choice experiment to study individual preferences for COVID-19 vaccines in the US. A unique characteristic of the microdata (N = 5671) is that the survey was conducted in five distinct waves from October 2020 to October 2021. Because of this dynamic feature, it is possible to control for evolving pandemic conditions such as the number of COVID-19 active cases, vaccination uptake, and the frequency of Google searches related to the vaccines. Furthermore, we employ a hybrid choice model to incorporate respondents' attitudes related to their perceived vulnerability to diseases, as well as their perceived health status. The hybrid choice model was extended to incorporate latent classes as well as random effects. We find that the rate of vaccinated individuals in the population actually increases the probability of vaccine hesitancy, and therefore may discourage people to get vaccinated. This may be evidence of free-riding behavior. On the other hand, the number of COVID-19 cases has a positive effect on the probability of getting vaccinated, suggesting that individuals react to the pandemic conditions by taking some protective measures. Google trend data do not seem to have a straightforward effect on the vaccination demand, but it increases consumers' willingness to pay for several vaccine characteristics. With respect to the analyzed attitudes, we find that perceived uninfectability is a significant driver of vaccine hesitancy, probably related to the frequent "natural immunity" argument. In turn, germ aversion has a positive effect on the probability of getting vaccinated as well as on the marginal willingness to pay. Finally, health status has a limited effect on whether the individual will decide to vaccinate or not.