The advent of COVID-19 vaccination meant a moment of hope after months of crisis communication. However, the context of disinformation on social media threatened the success of this public health campaign. This study examines how heads of government and fact-checking organizations in four countries managed communications on Twitter about the vaccination. Specifically, we conduct a content analysis of their discourses through the observation of propaganda mechanisms. The research draws on a corpus of words related to the pandemic and vaccines in France, Spain, the United Kingdom, and the United States ( n = 2,800). The data were captured for a five-month period (January-May 2021), during which COVID-19 vaccines became available for elderly people. The results show a trend of clearly fallacious communication among the political leaders, based on the tools of emphasis and appeal to emotion. We argue that the political messages about the vaccination mainly used propaganda strategies. These tweets also set, to a certain extent, the agendas of the most relevant fact-checking initiatives in each country.