COVID-19 vaccine: factual reporting, dynamic preferences, and gender hesitancy

At different rates in different countries, one can observe the phenomenon of COVID-19 vaccine hesitancy. In June 2021, we surveyed 1,068 people in France and Italy to inquire about individual potential acceptance, focusing on time preferences, in a risk-return framework: getting the jab today, in a month, and in 3 months; perceived risks of vaccination and COVID-19; and expected benefit of the vaccine. We conducted a randomized controlled trial to understand the impact of daily stimuli, such as factual news about vaccines, on audience acceptance of vaccination. In the main experiment, participants were asked to read two different articles extracted from two Italian newspapers about vaccine-related thrombosis, one using a more abstract description and language and the other using a more anecdotical description and concrete language. We find that individual preferences for vaccination are variable and unstable over time, and individual choices of accepting, refusing, or delaying may be affected by the way news is written. To understand these dynamic preferences, we propose a new model based on seven categories of human behaviours that was validated by a neural network. We observe a treatment effect: participants who red the articles significantly shifted to vaccine hesitancy categories. Furthermore, we detect a peculiar gender effect, showing that the type of language that results in a higher vaccination rate for men is correlated with women’s lower vaccination rate and vice versa. This outcome should be taken into consideration for an appropriate gender-based communication campaign to achieve herd immunity.