Vaccine hesitancy: an evolving challenge

In 2015, WHO defined vaccine hesitancy as a “delay in acceptance or refusal of vaccines despite availability of vaccination services”. More recently, it has been argued that the concept should be redefined as a “psychological state of indecisiveness that people may experience when making a decision regarding vaccination”, thereby distinguishing hesitancy from the final vaccination decision. Indeed, although hesitancy remains an internal state of indecision preceding the behavioural outcome related to vaccination, it is the actual choice a person makes about vaccination (ie, acceptance or refusal) that represents the behaviour itself. In this view, hesitant individuals might still decide to get vaccinated—a known phenomenon, especially in the context of the COVID-19 pandemic, when the concept of hesitant adopters emerged. Moreover, vaccine decision making is a dynamic process, influenced by time, place, vaccine type, and epidemiological context. [...]