A 2-arm cluster randomized controlled trial will be conducted with 450 trans women to assess the effectiveness of the Trans Women Connected mobile app. The Trans Women Connected intervention will address the unique needs of transgender women and the lack of evidence-based, transgender-specific HIV prevention. It is a mobile app delivered sexual health promotion program that engages transgender women through a strengths-based approach to HIV prevention and sexual health that uses the power of social networks to identify and encourage protective factors that support the health of transgender women. This approach recognizes the social and structural barriers that transgender women face. In the context of these barriers, which include stigma and discrimination in a number of interconnected spheres, individually-focused behavioral interventions are insufficient. This intervention takes a more comprehensive approach that intentionally targets community strengths and challenges. The mobile app will include more than 30 interactive activities including resource maps, PrEP content, post-exposure prophylaxis (PEP) content, and communication forums.

To be eligible, participants will be required to self-identify as transgender women; report having had 2 or more sexual partners in the past 90 days with at least one of those partners having a penis; be age 18-49 at baseline; own a smartphone; and reside in any state in the United States. Those in the treatment arm will be provided with the Trans Women Connected app, to be downloaded to their own device, and asked to use it during a month period. Those in the control arm will be asked to download a general health app and use it during a month period. Participants will complete brief online surveys at baseline, immediately following the app-use period (1-month post baseline), and at 3- and 6-months following baseline.

Participants will be recruited using a variety of methods, including: 1) Regional transwomen recruitment/retention specialists who are responsible for facilitating recruitment in their regions, addressing study questions, and maintaining connections with each participant to support study engagement; 2) Organizations. Organizations from across the U.S., at least one per state, that serve transgender women will be approached to help recruit participants through social media and in-person. 3) Google Adwords. Placing study advertisements on Google based on keyword for participant recruitment has been shown to be effective. 4) Social Media Advertising including targeted advertising on social media sites (Facebook/Instagram) and sponsoring study posts with social media influencers in the Transwomen community. Social media advertising has been shown to be favorable in terms of its cost-effectiveness, usability, and reach, especially with hard-to-reach populations, young adults and lesbian, gay, bisexual, and transgender (LGBT) populations. 5) Participant Recruitment (participants sharing information about the study within their networks). Participants will complete 4 web-based surveys and will receive $20 for baseline survey, $20 for an immediate posttest, $40 at 3-month follow up, $60 at final 6-month follow up.

Randomization. The 2-arm randomized controlled trial involves randomizing individual participants using an equal allocation (allocation ratio 1:1) to receive the full TWC app or an attention control app. Participants were randomized after completing their baseline surveys using the randomizer feature of Qualtrics.

Data Collection. Participants will be surveyed at 4 time points. 1) before randomization, 2) after using the mobile app for 1 month, 3) three months after completion of the baseline, and 4) six months after completion of the baseline. Surveys will be completed online through emailed or texted links. Data will also be collected through the apps. This includes usage data, such as what activities participants used and for how long, and process data, which includes content on the communication forum, text answers in the app, and visual content such as vision boards. Participants will receive an incentive of $20 for the baseline and immediate post-intervention survey, $40 for the 3-month follow up survey, and $60 for the 6 month follow up survey.

Study Hypotheses. Primary Hypotheses 1 (representing sexual health risk reduction through engagement in care 1) Women in the intervention group will report more STI testing (higher rates of STI testing in the prior 90 days) than the comparison group. Primary Hypotheses 2, women in the intervention group will report fewer acts of receptive condomless anal intercourse or condomless vaginal intercourse. Secondary Hypotheses (representing other important sexual health risk, and psychosocial outcomes):1) Participants in the intervention group will report reduced sexual risk taking including fewer acts of receptive condomless anal intercourse or condomless vaginal intercourse; greater use of condom use at last intercourse (receptive anal or vaginal); and increased use of PrEP for those that are HIV- 2) Participants in the intervention group will engage more with proactive health care and report more health care visits. 3) Participants in the treatment group will report more connectedness with other transgender women, including perceived social support and engagement with a mentor. 4) Participants in the intervention group will report greater efficacy in having safer sex and in communication both with partners and health care workers. 5) Those in the treatment group will have greater acceptance of their gender identity/comfort with gender identity.