Women are disproportionately at risk of acquiring HIV in East and Southern Africa, despite global declines in incidence. Female-initiated HIV prevention methods, like the dapivirine vaginal ring, are needed to end the HIV epidemic. In-depth interviews and focus groups retrospectively explored peer influence on acceptability of and adherence to the ring during the ASPIRE trial, a phase III placebo-controlled trial. Results were analyzed using an inductive analytic approach. Study participants (peers) of all ages and adherence groups developed important interpersonal connections and reported being more open and honest with each other than with external peers or study staff. Study peers who knew each other prior to joining appeared to have a stronger influence on each other's adherence than peers who met in the study. External peers provided primarily negative input about the ring and study, which sometimes led to ring removals. Peers' influence on each other's behavior in both prosocial and detrimental manners could have repercussions on adherence to a biomedical intervention, and consequently, individual disease risk and clinical trial outcomes. Future ring demonstration and implementation studies could use peer networks to intentionally influence uptake and adherence to the ring.
