Sudden Unexpected Infant Death Case Registry for Cook County, Illinois: Surveillance and Prevention (Comp A and C) - Sudden unexpected infant death (SUID) is a major cause of infant death and a public health issue with little progress over the past 20 years. After an initial decline in SUIDs following the 1992 policy statement by the American Academy of Pediatrics and the 1994 NIH-led “Back to Sleep” campaign, the number of SUIDs has plateaued, and nearly ten infants a day die suddenly and unexpectedly. As a recipient of SUID Case Registry funding beginning in 2019, we have established a successful surveillance system for SUID in Cook County, IL. Cook County is a widely diverse population of 5.2 million, the second most populous county in the United States that includes all of Chicago, the nation’s third largest city. As evidenced by this surveillance system, nearly every week in Cook County an infant dies suddenly and unexpectedly, with SUID rates that are over 14 times higher in non-Hispanic Black infants and nearly 3 times higher in Hispanic infants, when compared to white infants. Continuing surveillance through the established Cook County SUID-CR will allow for ongoing high-quality data collection, analysis and dissemination of the circumstances and factors regarding an infant’s sudden and unexpected death to inform prevention efforts. This is accomplished through our strong partnerships with the Cook County Medical Examiner’s Office and Cook County’s Child Death Review Teams, as well as the city, county and state’s public health departments. We have successfully developed prevention approaches to Cook County communities most impacted by SUID through our Community Partnership Approaches for Safe Sleep – Chicago team (CPASS Chicago). Our expanded public health and community outreach partners and activities will continue to be informed by the Cook County SUID-CR to tailor prevention approaches that address both the upstream factors driving disproportionate infant mortality experienced by historically disinvested communities as well as optimizing the immediate risks posed by the infant sleep environment.