Increasing prebunking effectiveness to aid disinformation-susceptible publics in overcoming vaccine-related disinformation.

In the dynamic intersection of health communication and disinformation, this study investigates tailored intervention strategies for disinformation-susceptible public segments classified by the motivation-knowledge-attitude framework. Using a two-phase survey and experimental design with American adults, participants were segmented into four public types (disinformation-immune, vulnerable, receptive, and amplifying) and exposed to one of three inoculation message conditions: autonomy supportive, autonomy controlling, or control. Data were analyzed using ANCOVA with Bonferroni-adjusted post-hoc comparisons to examine main and interactive effects of public segment and message type on motivational threat, autonomy support, and perceived message effectiveness (PME). Both inoculation message types elicited significantly higher motivational threat than the control (p < .001), with disinformation-vulnerable and amplifying publics reporting the highest levels overall (p < .001). Both inoculation conditions were perceived as significantly more effective than the control (p = .007 and p = .001, respectively). A significant interaction between public segment and message type was identified (p = .005), driven primarily by disinformation-immune publics, who rated both inoculation messages significantly higher in PME than the control (p < .001), while no significant message type differences emerged among other segments. These findings underscore the importance of audience segmentation in inoculation campaign design and offer practical guidance for health communication professionals crafting strategies to combat vaccine disinformation.