The Critical Role of Social Networks in Fueling Vaccine Hesitancy during the Covid-19 Pandemic

Individuals' decision-making processes related to vaccination play a crucial role in controlling infectious diseases, as evidenced by the Covid-19 pandemic. Vaccine hesitancy—defined as the delayed acceptance or refusal of vaccines despite their availability—has been identified as one of the top 10 global health threats. Understanding the factors and mechanisms driving vaccine hesitancy is essential for designing more effective intervention programmes. This study investigates how misinformation related to Covid-19 spreads through social networks and its impact on vaccination decisions.

Using a mixed-methods approach, the study combines a systematic review of existing literature with the analysis of large-scale social media data and the application of agent-based models (ABM). Over 5 million tweets from the early months of the pandemic were analysed, revealing significant politicisation of health issues, which led to clear divides on key topics such as vaccines and preventive measures.

The analysis identified social bots as key amplifiers of misinformation, intensifying polarisation, particularly among individuals with extreme ideologies, low socioeconomic status, and high religiosity. Agent-based simulations further demonstrated that network structure and the centrality of certain agents play crucial roles in the diffusion of vaccine-related opinions. Notably, anti-vaccine communities exhibited high levels of reciprocity among members, making it particularly difficult to counter misinformation and implement health promotion interventions within these groups.

This study concludes that vaccine hesitancy is heavily influenced by social network structures, misinformation sources, and the specific topics under debate. To enhance vaccine acceptance and control infectious diseases, it is critical to better understand these dynamics and tailor intervention programmes accordingly. The findings underscore the need for targeted efforts to address misinformation and polarisation in online social networks, particularly within communities resistant to vaccination.