Principal Findings
primary HIV prevention, sexual behaviors, MSM
In this randomized controlled trial, we found that a web-based intervention with a harm reduction approach could enhance the self-efficacy of MSM in refusing risky sexual behaviors and chemsex. The intervention enhanced HIV testing but had no effects on other STI testing. Importantly, we found that the intention of MSM to engage in chemsex and their actual engagement in chemsex can also be reduced by the intervention. However, it should be noted that, given the small sample size of participants who reported engaging in chemsex in the last 3 months during the follow-up interviews, the findings related to condom use might not be reliable and should be interpreted with caution. Nonetheless, the clinical significance and academic merits of the findings are substantial because this study has provided one of the very first pieces of evidence on the effectiveness of eHealth interventions in reducing the sexual harm of chemsex among MSM, which echoes the recent review by Strong and colleagues [The intervention in the current trial was developed through a harm reduction approach because most qualitative evidence suggests that many MSM prefer reducing the harm associated with drug use (eg, by learning how to better manage their use) instead of abstaining altogether [Compared with the control group, the intervention group demonstrated statistically significant effects on the primary outcomes with a small-to-moderate effect size (in Even though PrEP has provided a new means of harm reduction (ie, primary HIV prevention) in the context of chemsex [Another important benefit of the current study is that the intervention was found to reduce the participants’ intention to have chemsex and their actual engagement in chemsex. Given that chemsex tends to be hidden and private and that those who practice chemsex are difficult to reach [This study found no significant effect on other STI testing, implying that future interventions should strengthen the components intended to encourage MSM to undergo regular STI testing. Nonetheless, the negative result could be explained by the substantial reduction in the availability of sexual health services during the COVID-19 pandemic [