HIV pre-exposure prophylaxis (or PrEP) is an effective additional preventative measure for reducing the risk of HIV transmission. To address low levels of uptake, there is a need for public health interventions to increase target populations' awareness and willingness for adopting PrEP. One potential solution may be to incorporate a network intervention, which utilizes the connections between individuals to facilitate health behavior. This project examines how online networks can influence PrEP adoption intentions among gay and bisexual men through a mobile app-based experiment. In this study, participants will be randomly assigned into a social support condition or information-only control. Both conditions will involve an information component consisting messages aimed to address awareness, knowledge, and perceived barriers of PrEP adoption. However, those in the social support condition will also have an online chatting tool where they can discuss topics surrounding PrEP.

The primary objective of this study is to test the effectiveness of the mobile app intervention in increasing participants' knowledge/attitudes/intentions to initiate PrEP.

The secondary objective of this study is to determine the mechanism of the intervention through mediation analyses.

Roughly 1.7 million people worldwide are infected with HIV each year (UNAIDS, 2017). HIV pre-exposure prophylaxis (or PrEP) refers to taking a daily oral medicine to reduce the risk of contracting HIV. Known by the brand name Truvada or Descovy, PrEP is an effective additional preventative measure for reducing the risk of HIV transmission. To address low levels of uptake, there is a need for public health interventions to increase target populations' awareness and willingness for adopting PrEP.

One potential solution may be to incorporate a network intervention, which utilizes the connections between individuals to facilitate health behavior. In particular, online networks can provide anonymous support that transcends geographical boundaries (DeAndrea, 2015). Stigmatized behaviors, such as the adoption of PrEP, may greatly benefit from interventions that utilize online networks. This project examines how online networks can influence PrEP adoption intentions among gay and bisexual men through a mobile app-based experiment.

There are several ways in which online networks may influence health; however, social support may serve as the primary mechanism that influences PrEP adoption. In the context of HIV prevention, social support has generally reduced HIV-related risky behaviors (Qiao, Li, & Stanton, 2014). Thus, it is important to consider social support as a factor than can influence one's intention to adopt PrEP.

This field experiment will randomly assign participants into a social support condition or information-only control, and then randomly assign them into homophilous, clustered six-member peer networks. Both conditions will involve an information component consisting messages aimed to address awareness, knowledge, and perceived barriers of PrEP adoption. Social support will be operationalized through an online chatting tool where participants can discuss topics surrounding PrEP.

The primary objective of this study is to test the effectiveness of the mobile app intervention in increasing participants' knowledge/attitudes/intentions to initiate PrEP.

The secondary objective of this study is to determine the mechanism of the intervention through mediation analyses.

Inclusion Criteria:

• Gay or bisexual male
• Aged 18 and 35
• HIV-negative
• Not on PrEP
• Using an Android smartphone

Exclusion Criteria:

• Already participating in another HIV-related study.
• Not able or willing to carry an Android smartphone.

Must identify as male and be assigned male at birth.

Individual participant data will not be shared with other researchers.