This study investigates the emergence of a social identity among individuals critical of COVID-19 vaccine policies in France. Amidst concerns over potential restrictions and obligations linked to the vaccine, a collective of individuals has convened both offline and online to vocalize their dissent and affirm their autonomy in vaccination decisions. Perceived as deviant by mainstream media, government, and society at large, this analysis explores the group’s emerging identity in response to unfolding events.

Using computational analysis of tweets spanning the year following the vaccination campaign, this research explores how metrics including cosine similarity, pronoun usage, and outgroup labeling elucidate the emergence of social identity. Our findings reveal a pivotal shift in user engagement and identity dynamics following President Macron’s announcement mandating vaccination for health workers. Our results showed significant changes in linguistic patterns, suggesting the crystallization of a social identity in response to rejection.

Furthermore, we identify a core group of proficient and consistent users who play a central role in fostering group cohesion. A focused examination surrounding Macron’s speech unveils how new entrants adapt their linguistic expressions to align with the emergent group identity. These findings shed light on the intricate mechanisms driving social identity formation amidst contentious public health policies, offering insights into the dynamics of online discourse and collective action.