RESUMO
Our objective was to analyze the sources, characteristics, tone, and content of the most viewed YouTube videos in Spanish about Covid-19 vaccines. In February 2021, a search was carried out on YouTube using the terms "Vacuna Covid," "Vacuna coronavirus," and "Vacuna Covid19." Associations between tone, source, and others variables (e.g. number of views or dislikes) were studied with a Mann-Whitney U-test and a chi-square test. A total of 118 videos were analyzed; 63.6% were originated from Mexico and the USA; media created 57.6% of the videos. Positive tone was observed in 53.4%. The most discussed topics were target groups for vaccination (38.9%) and safety (43.2%). The 68 videos produced by media accumulated 31,565,295 views (55.0% of views), and the 19 videos created by health professionals obtained 10,742,825 views (18.7% of views). A significantly smaller number of likes was obtained in videos of media compared to those created by health professionals (p = .004). Videos made by health professionals, compared to those of media, showed a greater positive tone (OR = 3.09). Hoaxes/conspiracy theories were identified in 1.7% of the videos. Monitoring that the information on YouTube about Covid-19 vaccines is reliable should be a central part of Covid-19 vaccination campaigns.