This study will use the Multiphase Optimization Strategy (MOST) to optimize an adaptive intervention that successfully navigates COVID-19 medically or socially vulnerable people through a continuum of prevention, care and treatment (CoPCT) modeled on the HIV CoPCT. The COVID-19 CoPCT starts with testing and continues with successful adherence to prevention or treatment guidelines to help prevent and/or treat COVID-19. The study will assess the effectiveness of Navigation Services compared to referrals in increasing COVID-19 testing and Brief Counseling in increasing adherence to the State of IL recommendations for COVID-19 prevention and treatment. The study will also examine the effect of Critical Dialogue on testing behavior among people who decline to be tested for COVID-19. The investigators will develop decision rules about what evidence-based-interventions work best for what types of people (e.g., those who test right away, versus decliners) and in what period of the COVID-19 continuum. Finally, the study will shed light on factors associated with testing and adherence to IL recommendations. Investigators will follow Community Based Participatory Research principles in implementing a sequential, multiple assignment randomized trial (SMART) design. Adjusting for possible 15% loss to follow-up, a total sample of 548 people who are medically and socially vulnerable to infection and poor outcomes with COVID-19 will be enrolled as the intent-to treat-sample. The investigators are confident that they can recruit this sample in St. Clair County, IL based on their previous experience and because the research team has established relationships with other service agencies in the community from which, in addition to CBHC, research participants will be drawn. The primary outcome is completion of the COVID-19 test within one week of the first intervention session. The study will include 3 stages in which participants will be randomized to one of two possible interventions as follows:

1. Eligible and consenting participants will be randomized to receive the first-stage intervention: Navigation Services (NS) or standard services (referral to testing and IL digital information brochure after testing). The primary outcome is completion of the COVID-19 test within one week of the intervention session.
2. Those who get tested will be randomized to receive the second-stage intervention: continue with NS or standard treatment or switch to Brief Counseling (BC). The outcome will be adherence to IL recommendations. For those testing positive, adherence means engaging in a 14-day quarantine, receiving medical care as needed and contact tracing. For those testing negative, adherence means social distancing and wearing masks.
3. Those who do not get tested will be randomized into their second-stage intervention to continue with NS or digital brochure or switch to Critical Dialogue (CD). The outcome will be completing COVID-19 testing within 1 week of the second stage intervention session. Those who complete the testing will then be randomized to either continue with NS or digital brochure or switch to BC. Those who do not get tested will be randomized to continued NS or digital brochure or switch to CD. The outcome will be adherence to NJ recommendations, as defined above. All variables will be measured using standardized measures selected from the National Institutes of Health (NIH) PhenX Toolkit.

For the primary aim of comparing effects of Navigation Services versus referral on testing behavior and IL recommendations adherence, using standard sample size formula for difference of two proportions, a total sample size of 466 subjects is needed to have 80% power at α=0.05 to detect a 10% difference in proportions, assuming 70% in the referral group will complete testing and adhere to specific IL recommendations. The 466 sample size has 85% to detect a difference of 15% in adherence rates to IL recommendations between two interventions.