Whereas Romanian health officials have launched two national human papillomavirus (HPV) vaccination campaigns, the uptake rate remained insignificant. Understanding local perceptions of the vaccine is necessary, as they could inform future educational programmes. Given that social media provide new opportunities to communicate about vaccination, this paper sought to explore the public's constructions of the HPV vaccine as they were expressed on Internet discussion forums.Twenty discussion forums, with a total sample size of 2,240 comments (2007-2012), were included. We conducted a thematic analysis with a focus on language, informed by a discourse analytic approach.Positive discourses relying on evidence-based arguments or cancer-related experiences battled with negative discourses that focused mostly on pseudo-scientific information and affect-based testimonials. Both camps made use of appeals to authority in order to provide powerful messages. Critics expressed high levels of mistrust in the health system and perceived the vaccine as dangerous, as part of a conspiracy, as unnecessary or as a promoter of promiscuity. By contrast, supporters considered the HPV vaccine to be helpful and criticized the irrationality of opponents. Ambivalence and uncertainty also emerged, along with criticism toward the suboptimal organization of the vaccination programmes. Findings highlight ways in which views about the vaccine are embedded in broader perspectives about science, the national medical system, society development and economic inequality.Online posts are likely to elicit fear and doubts around vaccination, which in turn may impair decisions. Findings indicate that targeted education campaigns are needed in order to address public concerns about vaccination.