You can't nudge into vaccination: Comparing the effects of nudge types and Covid-19 vaccination attitudes on vaccine willingness.

Nudges can be an effective strategy to promote vaccination. However, it is necessary to better identify the characteristics of nudges that produce the strongest effects and how they interact with individuals' attitudes. Here we sequentially test the effectiveness of three nudge characteristics (framing, nudge type, and presentation modality) and the role of participants' attitudes toward Covid-19 vaccination, social solidarity and authoritarianism in vaccination decisions. In studies 1-4, participants were presented with a nudge manipulating a target characteristic (e.g. positive/negative framing, nudge type) and measuring willingness to vaccinate and related variables compared a control nudge. Study 5 used a single combined nudge reflecting the combination of successful nudges in previous studies. Results over all studies show that nudging has unreliable effects while vaccine attitudes are more reliably linked to all measures of vaccines willingness. These results suggest that attitudes play a more reliable role on effective adoption of vaccinations.