As evidence grows for the effectiveness of antiretroviral pre-exposure prophylaxis (PrEP) for HIV prevention [1–6], complementary research on PrEP acceptability [7] and uptake [8–13] has gained prominence. In the USA, PrEP acceptability research has largely focused on men who have sex with men (MSM) [14], given the sustained burden of HIV incidence in this group [15]. Although this work has identified many individual factors associated with willingness to use PrEP, emerging research has also examined PrEP acceptability in light of MSM partnership dynamics [16–19]. Focusing on dyads is imperative: at least one third of HIV infections among US MSM occur within primary partnerships [20, 21], and relationship dynamics—including intimacy, commitment, and other interpersonal factors—demonstrably influence both HIV risk and protective behaviors [22, 23]. For example, prior studies report that many MSM in primary partnerships engage in condomless sex to express intimacy, and condom nonuse may be motivated by the desire to preserve these intimacy benefits [24–27].

In this issue, Gamarel and Golub examine how intimacy motivations for condom nonuse may affect willingness to use PrEP among MSM in romantic partnerships [28]. The team interviewed MSM who self-reported being in seroconcordant, HIV-negative primary partnerships; 90 % reported recent condomless anal sex with their primary partners and 34 % did so with an outside (non-primary) partner. Regardless of whether participants had condomless sex with an outside partner, intimacy motivations for condomless sex were significantly and positively associated with the intention to use PrEP, if PrEP were available at no cost. This association was absent among a separate sample of MSM without primary partners, indicating that the desire to express intimacy through condomless sex may play a unique role in PrEP uptake among MSM in romantic relationships.

Gamarel and Golub’s insightful work has several implications for further research. First, PrEP-protected sex and condom-protected sex may carry different interpersonal meanings within MSM partnerships, and research should examine these distinctions. Study participants who expressed concern about the intimacy-inhibiting effects of condoms were more likely to want PrEP, suggesting that PrEP may not affect intimacy in the same way. Identifying the different values that MSM couples place on exclusively PrEP-protected sex, exclusively condom-protected sex, dually protected sex (using PrEP with condoms), and sex without protection can help to inform PrEP outreach, education, and user support. The perceived opportunity to engage in condomless sex at lower risk may motivate PrEP uptake, as suggested by a study among serodiscordant MSM couples [19]. Further study is needed, however, to understand how attitudes toward PrEP-protected sex will influence PrEP uptake and behavior in MSM relationships.

Second, the focus on intimacy motivations brings attention to the potential “secondary” benefits of PrEP—namely, advantages beyond pure risk-reduction. From the user’s perspective, these may include opportunities to reduce HIV risk while retaining the potential benefits of condomless sex (e.g., intimacy, pleasure, and fertility); reduced HIV-related anxiety or fear [19, 29–32]; and increased control over sexual health [31]. Additional research is now needed to understand how PrEP users anticipate and experience these secondary benefits (if at all) and to incorporate this information into user support strategies.

Third, Gamarel and Golub’s findings highlight the need for couples-based approaches to PrEP implementation among MSM. Partners may be a source of support for PrEP use and adherence [16, 18, 33], but little research has investigated couples-based HIV prevention strategies for MSM [22, 34]. One study has tested a couples-based strategy to promote HIV medication adherence among MSM in serodiscordant partnerships [35], which may be adaptable to PrEP use. Several other MSM couples-based approaches show promise [36, 37]; research is now needed to extend dyadic interventions to PrEP decision-making, as well as sustained use among couples who choose to adopt PrEP.

Finally, the team’s emphasis on seroconcordant HIV-negative partnerships is a meaningful expansion of the PrEP acceptability literature. To advance this work, future research might investigate PrEP acceptability, uptake, and PrEP user experiences in the context of sexual agreements and shared decision-making. Intimacy is one of many relationship factors [23], and dyadic research is needed to understand how perceived intimacy and other partnership features (e.g., duration, communication, and trust) influence PrEP acceptability. Additional research could also explore sexual agreements as both facilitators and potential barriers to PrEP use; if, for example, an agreement prohibits sex outside a seroconcordant partnership, PrEP use may be viewed as evidence of violation, thereby complicating uptake or adherence. Gamarel and Golub’s findings also reinforce the need for PrEP providers to ask patients about both primary and outside partners when evaluating whether patients are at “substantial risk of HIV acquisition” [38], particularly when patients report being in a seroconcordant relationship.

PrEP offers a compelling new tool for HIV prevention in several populations, including MSM at risk of infection, and PrEP implementation efforts can benefit from a nuanced understanding of the contexts in which HIV risk and protective behaviors occur. The interpersonal dynamics of primary MSM partnerships are one such context. By identifying how intimacy motivations for condom nonuse may influence PrEP acceptability in this population, Gamarel and Golub have introduced an important set of research questions, as well as promising opportunities for maximizing PrEP’s preventive impact.