Sustaining Independent Public Health Surveillance: The C3 Cohort as a National Platform for Vaccine Behavior, Long COVID, and Emerging Health Priorities

Our team has been leading the national CHASING COVID Cohort (C3) study of SARS-CoV-2, which focused on the burden of disease, long COVID incidence, prevalence, and risk factors, vaccine beliefs, intentions, and uptake, and many other public health-related outcomes (e.g., food insecurity, mental health) since the beginning of the SARS-CoV-2 pandemic. The C3 study, with thousands of participants from all 50 US states, is uniquely positioned to characterize the duration, persistence, and burden of long COVID longitudinally, with follow-up currently out to 6 years, as of March 2026.

The C3 study represents an important opportunity to fill public health knowledge and situational awareness gaps and remains salvageable with over 3,800 participants engaged in the last funded wave of data collection completed in late August 2025.

We intend to routinely field 2–3 cohort data collection waves per year focused on: 1) measurement of vaccine knowledge, beliefs, and behaviors; 2) describing the burden of persistent long COVID and its determinants; and 3) measuring other timely public health measures to fill important surveillance gaps.

Aim: To maintain the C3 cohort infrastructure for data collection around vaccine beliefs, intentions, and uptake, with the ability for rapid collection, analysis, and dissemination of these and other critical public health topics.

Further follow-up of this cohort is warranted to gather vaccine outcomes during and after the 2025–26 respiratory season, including the effects of evolving vaccine communications and shifting guidance on vaccination behavior. We propose continued data collection (ideally 2–3 waves per year) with a budget for participant incentives per completed questionnaire and a core staff dedicated to maintaining cohort infrastructure, rapid data cleaning, analysis, and dissemination of results via preprints and peer-reviewed scientific manuscripts.