During health crises, misinformation may spread rapidly on social media, leading to hesitancy towards health authorities. The COVID-19 pandemic prompted significant research on how communication from health authorities can effectively facilitate compliance with health-related behavioral advice such as distancing and vaccination. Far fewer studies have assessed whether and how public health communication can help citizens avoid the harmful consequences of exposure to COVID-19 misinformation, including passing it on to others. In two experiments in Denmark during the pandemic, the effectiveness of a 3-minute and a 15-second intervention from the Danish Health Authorities on social media was assessed, along with an accuracy nudge. The findings showed that the 3-minute intervention providing competences through concrete and actionable advice decreased sharing of COVID-19-related misinformation and boosted their sense of self-efficacy. These findings suggest that authorities can effectively invest in building citizens’ competences in order to mitigate the spread of misinformation on social media.

Effective communication is essential for delivering public health messages and enabling behaviour change. Little is known about possible backfiring, or spillover effects, of COVID-19 vaccine messaging. In a study with n = 1,848 United Kingdom (UK) adults, we assess whether communication strategies that target vaccine hesitancy have any unintended, positive or negative, spillover effects on people's intention to engage in protective, compliance and prosocial behaviours. In June–July 2021, we conducted an online experiment to assess the potential spillover effects of three messages, emphasising (a) the medical benefits of COVID-19 vaccination, (b) the non-medical collective benefits of vaccination or (c) the non-medical individual benefits of holding a vaccination certificate. Exposure to different messages did not significantly affect people's intention to engage in protective, compliance, or prosocial behaviours. Instead, vaccination status (being vaccinated vs not) was positively associated with intentions to engage in protective, compliance and prosocial behaviours. Our results suggest that communication strategies that aim to increase vaccination uptake do not have any unintended effects on other health behaviours and vaccination campaigns can be tailored to specific populations to increase uptake and compliance.