"Despite detailed policies on mis- and disinformation and promises to enforce them, social media platforms are failing to tackle prominent groups and individuals who spread false claims about COVID-19 and vaccines online. Using the World Doctors Alliance1 as a case study, a group that has spread various problematic, false and conspiratorial claims about COVID-19 and vaccines, ISD found that 78% of the group’s 1.2 million online followers are found on mainstream platforms (Facebook, Instagram, YouTube, Twitter, TikTok) who claim to prohibit this kind of content. The Facebook pages of World Doctors Alliance members have a following of over 550,000 users, which increased by 13,215% between January 2020 and July 2021. Videos posted by these Facebook pages have been viewed more than 21.1 million times. These pages have accumulated a total of 5.77 million interactions since January 2020, with interaction rates increasing by 85% in the first six months of 2021 compared to the previous six months. Facebook posts mentioning the World Doctors Alliance or its members have attracted more than three million engagements on Facebook and are present in at least 46 different languages on the platform. ISD found that large proportions—often the majority—of the most engaged with content on Facebook mentioning the World Doctors Alliance or its members in English, Spanish, German and Arabic contained false, misleading or conspiratorial claims related to COVID-19 and vaccines. Organisations that are part of Facebook’s fact-checking program have debunked false claims made by the World Doctors Alliance 189 times since the beginning of the pandemic. Despite this extensive fact-checking effort, Facebook is failing to take decisive action on the group or its members. Facebook’s fact-checking program incorporates organisations from 115 countries, but there appear to be major gaps in fact-checking in non-English languages. ISD found minimal application of fact-checking labels across the four languages analysed, with lower application rates on posts in German, Spanish and Arabic than in English. Content that does contain fact-checking labels is still accumulating tens and sometimes hundreds of thousands of engagements." (Key findings)