The COVID-19 pandemic is being accompanied by the circulation of a large volume of information, partly misleading or false, a phenomenon known as “infodemic”. The profusion of information makes it difficult to identify reliable sources and can affect adherence to containment measures, such as vaccines. In this article, we investigated the 100 links about vaccines that generated the highest engagement on social media in 2020 and compared them with those with the highest engagement in 2018-2019, before the pandemic. The objective is to understand how infodemic affects the public debate on vaccination, how disinformation appears in these conversations, and what are the positions, emitters, and privileged themes. We found that the average engagement increased by 8.6 times and that the predominance of verified information remained before and during the pandemic. However, the engagement of disinformation has grown significantly and its profile has changed: if the false content, emitted by non-professional vehicles, predominated in 2018-2019, the information distorted by sensationalized headlines emitted by professional vehicles stands out in 2020. Besides, the political instrumentalization of the debate on vaccination, present in both contexts, draws attention to the relationship between disinformation and narrative disputes. These results point to the infodemic complexity and the need for strategies to combat disinformation that take into account the economic and socio-political contexts of the informative circulation on the networks