  One of the most important tools available to limit the spread and impact of
infectious diseases is vaccination. It is therefore important to understand
what factors determine people's vaccination decisions. To this end, previous
behavioural research made use of, (i) controlled but often abstract or
hypothetical studies (e.g., vignettes) or, (ii) realistic but typically less
flexible studies that make it difficult to understand individual decision
processes (e.g., clinical trials). Combining the best of these approaches, we
propose integrating real-world Bluetooth contacts via smartphones in several
rounds of a game scenario, as a novel methodology to study vaccination
decisions and disease spread. In our 12-week proof-of-concept study conducted
with $N$ = 494 students, we found that participants strongly responded to some
of the information provided to them during or after each decision round,
particularly those related to their individual health outcomes. In contrast,
information related to others' decisions and outcomes (e.g., the number of
vaccinated or infected individuals) appeared to be less important. We discuss
the potential of this novel method and point to fruitful areas for future
research.
