The study staff will conduct a hybrid type 1 effectiveness implementation 2-arm trail with 360 Black young adults from Alabama, Georgia, and North Carolina. Participants will be randomized to receive the standard of care (control) or the TT-C intervention arm, each with a balance of 180 participants. Primary effectiveness outcome is COVID-19 vaccine uptake define as receipt of any vaccine (primary series or secondary booster). Secondary effectiveness outcomes are vaccine hesitancy, confidence, and knowledge, attitudes, and beliefs. The study staff will also conduct qualitative interviews with a group of purposively selected AA-YA participants (est. n=12-16) and site staff (est. n=6-8) to assess barriers and facilitators to implementation. The hypothesis is that the intervention arm will be more effective than the control arm at increasing vaccine uptake.

The study staff will recruit and enroll 360 AA-YA from communities in Alabama, Georgia, and North Carolina. After collecting informed consent, participants will be randomized using block randomization to the control condition or TT-C (remote), each with a balanced 180 participants (N=360). The standard of care (SOC) control will be the provision of COVID vaccine materials from the CDC.

After screening eligible and agreeing to be contacted, eligible responses will be reviewed individually by study staff to determine authenticity and legitimacy. In addition to eligibility criteria, staff will review bot detection values as well as location based on IP address & latitude/longitude. If determined eligible, staff complete the Verification CRF and REDCap emails the individual with a unique consent form link to complete. Once completed, REDCap sends the baseline survey linked to their unique ID in REDCap.

After the baseline survey is complete, study staff will randomize the participant with the Randomization CRF to either the intervention or control group. Based on the study arm, study staff will either email the participant with the developed SOC materials or email the participant with a unique link to create their account for the TT-C app. If SOC, study staff will compensate the participant $50 for enrolling.

If participant is randomized to intervention arm, they will be prompted to create their account with the provided link, then will be directed to download and login to the TT-C app. Once account creation is confirmed in the administrator portal, study staff will compensate the participant $50 for enrolling.

TT-C arm: Once enrolled, participants will be emailed a unique link to create their TT-C account and instructions on how to download the TT-C (remote) app from the iOS or Google Play store. They will be asked to complete the intervention within one month. Participants will be compensated $50 for completing the baseline and reminded that they will be asked to return in 1 and 3 months for follow-up.

SOC arm: Research staff will provide COVID vaccine materials from the CDC to those participants in the SOC arm. Participants will be compensated $50 for completing the baseline and reminded that they will be asked to complete 1 and 3-month follow- up surveys. To provide the maximum benefit through this trial, after the completion of the data collection associated with the primary RCT, those randomized to the control arm who still report VH will be offered the opportunity to accept the TT-C intervention delivered remotely.

Inclusion Criteria:

• Identify as African American/Black
• Able to speak and read English
• Has access to personal smartphone
• Current resident of AL, GA, NC

Exclusion Criteria:

• Aged younger than 18 year or older than 29 years
• Does not identify as African American/Black
• Non-English speaking
• Does not live in Al, GA, NC
• Unable to provide informed consent
• Receipt of full COVID vaccine series (including vaccination and booster or prior participation in a vaccine trial)

Deidentified individual data that supports the results will be shared beginning 9 to 36 months following publication provided the investigator who proposes to use the data has approval from an Institutional Review Board (IRB), Independent Ethics Committee (IEC), or Research Ethics Board (REB), as applicable, and executes a data use/sharing agreement with UNC.

The results will be shared beginning 9 to 36 months following publication.

Requesting investigator has approved IRB, IEC, or REB and an executed data use/sharing agreement with UNC.

Adverse event data was collected during the time participants were enrolled. Intervention participants for 3 months; Standard of Care (Control) for 3 or 6 months depending on if they received the app later on.