Discussion
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The findings from this study underscore the high acceptability of and adherence to RM products for HIV prevention among participants living across six different countries. Participants’ adherence complied with the protocol expectations (i.e., participants were to use the product at least once a week if they did not engage in RAI). Using latent class trajectory analyses, we were able to understand differences in participants’ RM use trajectories using their SMS self-reports. Similar to prior research on rectal gel use for HIV prevention among transgender women and MSM [The differences observed across trajectories suggest moving away from one-size-fits-all approaches, as participants’ frequency of use over time varied based on their sociodemographic and behavioral characteristics. For example, participants in the ‘protocol compliant trajectory’ group were more likely to live in the US, where PrEP is more readily available, and to self-report PrEP use than those in the ‘high use trajectory’ group. Participants in the ‘high use trajectory’ group, on the other hand, reported higher intentions to use RM in the future if it protected against HIV and were characterized as having greater educational attainment than peers in the ‘protocol compliant trajectory’ group. Given these findings, there is a need to address the variability in product use over time as future RM and other HIV prevention trials are undertaken. Future research should invest in the development and testing of interventions that account for individuals’ variability in their sociodemographic characteristics (e.g., education, geographic region where they live, access to PrEP), and leverage participants’ psychosocial constructs (e.g., intentions to use RM in the future) to promote product use and adherence.This study had several strengths and limitations deserving mention. First, this is the first study to examine the systematic use of these three promising placebo RM modalities for rectal drug delivery prior to RAI and examine participants’ experiences with all three products. Examining each product’s use in real life contexts strengthens the social validity of our findings and the potential use for these three modes of delivery in the future. As a limitation, however, we were unable to collect SMS data from all participants. While we included these participants as their own group in our analyses, it is unclear what trajectory they would have belonged to had they provided SMS data. Second, due to the use of placebo RM modalities, it is unclear whether the trajectory and acceptability of placebo RM modalities match those of actual RM modalities had an active drug been administered. Third, our ability to recruit and retain a large sample of young SGM living in geographically and socio-politically diverse countries is noteworthy and strengthens the generalizability of our findings to diverse contexts. Unfortunately, we are unable to run country-specific analyses given the limited sample size within each country. Given the variation in structural and cultural contexts, such as the state of their healthcare systems, social norms, perceptions of HIV and various prevention methods, and acceptance of SGM, future research examining how these contextual factors influence participants’ use and adherence to study products is warranted. Fourth, the prospective collection of weekly SMS-facilitated data from participants allowed for the modeling of the product use trajectories. While self-reported data may be biased because of recall and social desirability issues, we believe that recall and social desirability biases were minimized through the on-site training using the SMS system, including how to protect participants’ privacy, and participants’ ability to verify their entries at each PUEV. Moreover, this analysis examines product use with RAI and at least once per week if participants did not have RAI in a given week. At present, we are unable to assess whether participants’ sexual behavior trajectories are associated with their assigned product utilization trajectory. Finally, COVID-19 might have mitigated participants’ adherence to RM products. Some participants encountered the start of the COVID-19 pandemic during the course of the study. While we minimized interruptions to our trial and ensured that rigor was preserved during the COVID-19 pandemic (Jacobson et al., 2022), we are unable to assess how participants’ sexual behaviors may have changed due to COVID-19 social distancing protocols.