This C3 project, Community network-driven COVID-19 testing of vulnerable populations in the Central US, will implement and evaluate a COVID-19 testing approach that combines an evidence-based Social Network Testing Strategy (SNS) with community developed COVID-19 public health messages (SNS+). C3 will engage two disenfranchised populations across rural and urban sites in states across the Central US (TX, LA, AR, IN, IL). C3 leverages NIDA's Justice Community Opioid Innovation Network (JCOIN), the PIs' extensive community located COVID-19 testing programs, and a network of established community partnerships. The collaborative community-academic partnerships, research and engagement infrastructure, and team's leadership across JCOIN will ensure that C3 can rapidly recruit, enroll and test most disenfranchised community members, (n=2400) and through this process, accelerate any forthcoming COVID-19 public health prevention interventions. C3 focuses on two communities most impacted by COVID-19: 1) Criminal justice involved (CJI) - non-incarcerated people with previous history of arrest/jail/prison, probation/parole and drug- court attendance; and 2) Low-income Latinx - community members at 250% or below Federal Poverty Level. Both of these diverse populations, and the overlap between them, have some of the highest rates of COVID-19 infection and death in the United States. Messaging that affirms individual agency and corrects misinformation, combined with accessible and acceptable testing, is required to accelerate COVID-19 prevention for these populations. We use contextually adapted and theory-driven messages – misinformation correction and self- affirmation – to increase awareness, self-efficacy and community engagement in our adapted testing strategy – the Social Network testing Strategy (SNS). SNS is an evidence-based testing intervention that has been widely used in multiple settings with marginalized individuals (ie substance-users) who facilitate the recruitment of their social contacts into testing services. SNS combined with theory-driven, contextually appropriate COVID- 19 messaging (SNS+) will address challenges to current COVID-19 testing strategies which are limited by misinformation, stigma, distrust, and limited affirmation of ability to prevent COVID-19. C3 in partnership with community will: Develop COVID-19 messages that emphasize self-affirmation and misinformation correction for implementation in SNS; Test the efficacy (number of network members COVID-19 tested) of a combined SNS-messaging (SNS+) intervention versus standard SNS using adaptive randomization; and Evaluate C3 implementation strategies and key implementation outcomes (ie cost) using the RE-AIM framework. The disenfranchised populations to be engaged in C3 reflect those most impacted by COVID-19 and least able to adopt COVID-19 prevention practices. C3 is “shovel-ready” for implementation in the short timeframe of the RADx-UP mechanism, with significant institutional...