What happens when the CDC stops posting about measles on social media? An exploratory analysis of social media coverage during the 2025 measles outbreak.

Amidst the nation's largest measles outbreak in 30 years, the Centers for Disease Control and Prevention (CDC)'s social media accounts have gone quiet, creating a "void" in online health communication. In this vacuum, measles messaging has been dominated by news media rather than expert health authorities, resulting in polarized and potentially inaccurate information. In this exploratory study, we analyzed social media content around measles and MMR vaccines on Facebook, Instagram, and X. We observed an emerging "health communication void" around measles: the CDC posted only 10 times total, across the 3 platforms, in the first 8 months of 2025, down from an average of 45.8 posts over the same period from 2021 to 2024, despite fewer measles cases. Major news media outlets averaged 40.4 social media posts in the same period of 2025, with post frequency closely mirroring trends in measles cases. This shift in messaging may impact the public's situational awareness and further erode vaccine confidence.