People occasionally could choose between various COVID-19 vaccines, with some perceived as superior to others. We examined how the availability of an inferior vaccine influences the intention and behavior regarding the superior vaccine and overall vaccine uptake. (2/4)

Across two preregistered studies (total N = 2,484), we found evidence of a decoy effect: the intention to get vaccinated with a superior vaccine (target) increased when an alternative was available that was either less effective or had more severe side effects (decoy). (3/4)