The erosion of public trust in health information and government communication, particularly during crises like the Covid-19 pandemic, highlights a critical challenge in how health policies are transmitted and received. This study examines the dramatic shift in public sentiment toward Covid-19 vaccination in South Africa during 2021, a period that saw a decline from initial high acceptance to significant hesitancy. We argue that a process of social media selection allowed extreme views to proliferate as official sources retreated. Our findings suggest that sustained or increased mainstream media engagement, particularly from official sources like government and health authorities, could have mitigated the dominance of anti-vaccine narratives and have crucial implications for government communication and public health policies in the digital age. We collected and classified 482,450 original tweets about vaccination. We show that, by the end of 2021, Twitter activity was characterized by a progressive surge in anti-vaccination tweets and a decline in pro-vaccination and factual information, particularly from mainstream media. This shift mirrors the decrease in actual vaccination rates. Employing agent-based modeling, we simulated counterfactual scenarios to assess the impact of media presence on vaccine discourse. The results indicate that sustained or increased media engagement could have mitigated the dominance of anti-vaccine narratives. Conversely, a simulated media downturn led to a steeper decline in pro-vaccination content. The findings suggest that mainstream news media play a crucial role in shaping public perceptions of and support for health policies and that their disengagement creates an informational void exploited by misinformation.
Morselli et al. (2025) studied this question.