Referral Link SST Delivery Arm (RL-SST Arm)
Index MSM in this arm initially received a web-based identifiable SST referral link instead of physical SST packages, which could be shared with up to three alters after baseline survey. The referral links facilitated a free express delivery of SST packages and collection of the following information from alters: a preferred name (or an alias), a phone number, and post address. Each link would expire after three uses. Each alter could only apply for one SST package with the link, which could be accessed by only one device (both a WeChat account and a phone number).