The vaccination campaign against COVID-19 in Brazil took place amid the politicization of the pandemic and controversies in the acquisition and application of vaccines. One of these main controversies concerns childhood vaccination against SARS-CoV-2. In this context, we analyzed the profiles organizing the posts, the themes, positionings, and arguments about childhood vaccination mobilized on Facebook and Instagram in Brazil from 2020 to 2022. Using descriptors associated with childhood immunization, we identified 1,985 posts that addressed the subject in these two social media. From the analysis, we observed the predominance of favorable and neutral positions in approaching the subject, which was mainly guided by media outlets and profiles related to public authorities and thematically based on the discussion about the childhood vaccination campaign and the politicization of the vaccine. We also identified that the subject sparked the production of arguments around the safety and effectiveness of immunization agents, the need to protect children, freedom of decision-making for families, and the interference of political issues in the child vaccination process.