Political communication has been extensively studied through both the broader context of societal and political systems, as well as through the lens of mediatization, which emphasizes the intersection of political and media logics. Within this framework, scholars originally identified three distinct stages or eras of political communication. However, recent scholarship has increasingly focused on the transition to a “fourth” era, characterized by the growing impact of digital and social media. This shift, from the “television age” to the “social media age”, has not only introduced new media channels for conveying political messages but has also fundamentally transformed the nature of political communication itself—shifting from top-down, centralized models to more horizontal, decentralized forms of interaction. Current research on the role of social media in political communication reveals a complex landscape. These platforms appear to both enhance and undermine established processes of political deliberation. On the one hand, they provide new avenues for civic engagement and political discourse, while on the other, they contribute to issues such as disinformation, polarization, and the erosion of privacy. This entry aims to offer a comprehensive review of how social media platforms have reshaped the dynamics of political communication and civic participation. It further explores the challenges that accompany these transformations, such as the spread of disinformation, rising political polarization, increasing incivility, and privacy concerns stemming from advanced digital marketing techniques in political contexts.

Purpose The distinction between beliefs and facts, as well as between science and pseudoscience, appears to be hazy in the post-truth era. This study draws inspiration from public discourse concerning the safety of COVID-19 vaccines during the pandemic, aiming to explore the narratives of COVID-19 vaccine skeptics within the Greek online public sphere. Methodology For the purposes of our study, we analyzed Facebook posts from users’ pages and public groups during a three-month period (from September 2021 to November 2021), focusing primarily on content related to COVID-19 vaccination. By employing thematic analysis, we investigated the main themes upon which the anti-vaccination camp bases its rhetoric and the sources it uses to justify its claims. Findings Our findings suggest that in the Greek online context, the anti-vaccination discourse, as expressed on Facebook platform, is an amalgam of distrust towards institutional actors (politicians, the medical community, legacy media, the establishment in general) and concerns regarding the safety/complications of COVID-19 vaccination itself. Social implications Our study contributes to the existing body of academic literature addressing the impact of social media platforms on public opinion related to health matters. It underscores the potential and challenges associated with the unregulated dissemination of information within polarized digital contexts. Originality/value This study sheds light on the distinctive characteristics of anti-vaccine rhetoric, as expressed on social media, within the context of Greek society. It offers insights to scholars and researchers interested in the dynamics of social media discourse and its implications for public health communication.

Traditional news media have long been the primary source of information on environmental issues, influencing public perceptions and shaping discourse on ecological sustainability. Media representations play a central role in forming public opinion, especially on climate change, which has become a highly politicized and polarized topic, both offline and online. Political ideologies, economic interests, and government agendas significantly shape how the public discusses and responds to strategies for addressing climate change. This study focuses on the most engaging environmental content posted on social media and explores whether climate change is the dominant topic in these discussions. It also examines which actors (e.g., politicians, institutions, citizens) and sources (legacy media or alternative media) are featured in the most popular content. The aim is to identify the factors that drive user engagement on platforms like Facebook, Twitter (now X), and YouTube, and to investigate how social media users contribute to the plurality and diversity of voices shaping the discussions on environmental issues. The study considers whether these platforms support the democratic potential of public debate. Over a three-month period (Sept.–Nov. 2021), the study monitored social media and compared non-professional user’s posts with professional content from legacy media. The findings show that institutional actors dominate the online debate on environmental issues and climate change. Facebook engagement largely revolves around content from organizations and politicians, while Twitter users refer to organizational sources. On YouTube, however, local and regional media content is more prominent. This is surprising since surveys suggest that Greeks mistrust legacy media and prefer social media for information, viewing traditional outlets as corrupt and biased towards the dominant class.

In the post truth era the limits between facts and beliefs, science and pseudo-science seem to be quite blurred. Social media platforms, such as Facebook, provide the ideal vehicle for the widespread sharing of misinformation, by fostering the creation of “filter Bubbles” and “echo chambers”. For the purposes of our study, we analyzed Facebook posts from users’ pages and public groups over a three – month period (from September 2021 to November 2021) with a primary focus on the vaccination against COVID-19. Using thematic content analysis, we attempted to explore the major themes that skeptics of COVID-19 vaccines use to justify their hesitancy. According to research findings, the anti-vaccination discourse on Facebook platform in Greece combines features such as mistrust towards politicians, the medical community, the legacy media, the establishment as a whole, and facts regarding the safety/complications of COVID-19 vaccination itself. If the medical society aspires to combat misinformation regarding health issues, then, deconstructing the anti-vaccination rhetoric will be a pivotal step for the ultimate survival of epistemological truths and scientific discourse in the public sphere.

Misinformation has emerged as a significant threat to both society and public health, with social media acting as a major conduit for its dissemination. This contributes to harmful health outcomes and undermines trust in authoritative institutions. In addition, the dismantling of scientific authority seems to be a symptom of the post-truth era, where “alternative facts” are presented in the public debate as indisputable evidence of the inherent limitations of scientific infallibility. The prevalence of misinformation on social media platforms stems from multiple, interconnected factors, including individual-level influences such as cognitive biases, as well as systemic aspects of social media’s information architecture. Unlike scientific institutions that adhere to the principles of evidence-based knowledge, social media platforms operate under an attention-driven model that favors virality over factuality. Addressing these challenges effectively requires coordinated, multi-level, and multidisciplinary interventions targeting users, content creators, technology companies, health authorities, and governments to restore public trust and safeguard the credibility of medical expertise.