Explaining Twitter’s inability to reduce vaccine misinformation during the COVID-19 pandemic

Users dissatisfied with exposure to objectionable online content have begun to migrate en masse to new social media platforms. These new platforms share architectural features with legacy platforms, but offer content moderation services that legacy platforms no longer employ at scale. Such migrations assume that moderation interventions, such as deplatforming and content removal, are efficacious; however, this claim has not been evaluated based on evidence. We therefore evaluated the efficacy of Twitter’s attempts to curtail vaccine misinformation during the COVID-19 pandemic. We found that vaccine skeptical accounts generated a larger share of tweets about vaccines, increased in virality, and became more misinformative after Twitter began removing content and accounts. We also found evidence that Twitter’s mass deplatforming of 70,000 accounts on January 8, 2021 preceded an increase in misinformation, calling into question the efficacy of these removals. Novel platforms that share Twitter’s architecture may therefore face similar moderation challenges.