ABSTRACT
BACKGROUND: Throughout the ongoing COVID-19 pandemic debunking misinformation has been one of the most employed strategies used to address vaccine hesitancy. We investigated whether - and for whom - debunking is effective or even counterproductive in decreasing misinformation belief and vaccination hesitancy. METHOD: We conducted a randomized controlled trial (N = 588) utilizing a real-world debunking campaign from the German Ministry of Health. We considered the condition (debunking vs. control) as between-subjects factor, assessed misinformation belief (pretest vs. posttest) as a repeated-measures factor and vaccination intention as a dependent variable. Preregistered subgroup analyses were conducted for different levels of a priori misinformation belief and general vaccination confidence. RESULTS: The analyses revealed differential effects on misinformation belief and vaccination intention in participants with low, medium, and high a priori belief: A debunking effect on misinformation belief (dRM = -0.80) was only found in participants with a medium a priori belief and did not extend to these participants' vaccination intentions. Among participants with a high a priori misinformation belief, explorative analysis revealed a small unintended backfiring effect on vaccination intentions (ηp2 = 0.03). CONCLUSIONS: Our findings suggest that debunking is an effective communication strategy to address moderate levels of misinformation beliefs, but it does not constitute a one-fits-all strategy to reduce vaccination hesitancy among the general public. Although countering misinformation should certainly be an integral part of public health communication, additional initiatives, which address individual concerns with targeted and authentic communication, should be taken to enhance the impact on hesitant populations and avoid backfiring effects.