With 675 confirmed cases of measles in Romania in September 2016, the Ministry of Health launched the online campaign called 'Vaccines Save Lives'. This study seeks to apply the Health Belief Model (HBM) constructs to the online communication among the Romanian Ministry of Health and online users throughout this vaccination campaign. Using a mixed-method approach, we demonstrate how cluster analysis can help in visualizing the overall relationship among codes (HBM constructs) in the thematic interpretation related to vaccination. Results of the cluster analysis show that the Romanian Ministry of Health used three main themes (shaping credibility, reality versus conspiracy, and unbiased information). Focusing on the diseases that vaccinations could prevent, the Romanian authority also addressed the issues related to conspiracy theory, the possible side effects, and collateral victims if parents refuse to vaccinate their children. The online users' comments were structured on two themes: multi-faceted reluctance and vaccination gain. Despite the anti-vaccination comments and anti-work-related content directed toward the campaign and the Ministry of Health, there were pro-vaccination comments in which online users encouraged parents to report cases of side effects and accused them of using their personal stories to provoke vaccination hesitancy. These findings may provide important information to (inter)national communication practitioners who design and implement health campaigns to increase vaccination rates.
Keywords: Romania; Vaccination; cluster analysis; health belief model.