The HIV epidemic was first described in Vietnam in the early 1990s (1), and in the last 30 years, the epidemic has spread to different parts of the country. Since 1999, HIV has been reported in all provinces and cities of Vietnam (2). Although men who have sex with men (MSM) have been recognized as a key population affected by HIV in different parts of the world (3), in Vietnam, they were only identified as a priority population for HIV prevention in the last decade (4), despite warning signs in the early 2000s that HIV was spreading in this population (5, 6).

A study conducted only in Ho Chi Minh City in 2004 reported an HIV prevalence of 8% in a sample of MSM recruited in MSM-specific venues (7). The first, national integrated biological behavioral surveillance (IBBS) conducted in 2006 reported that the HIV prevalence among MSM in Ho Chi Minh City and Hanoi was 5 and 9%, respectively (8). In the second IBBS conducted in 2009, HIV prevalence exceeded 10% in Hanoi (19.8%) and Ho Chi Minh City (14.3%), as well as in Haiphong (16.6%), the country’s third largest city (9), suggesting HIV prevalence had increased substantially among MSM in major cities across Vietnam. A more recent study found an HIV prevalence of 14.8% among MSM in Ho Chi Minh City (10). A better understanding of the individual, social, and structural factors that affect HIV risks is, therefore, needed to prevent further transmission of HIV in the MSM population in Vietnam.

Previous studies have found that HIV infection among MSM in Vietnam is associated with younger age, lower education and injecting drug use (7, 11), a higher number of recent sexual partners (5, 7), and sex work and inconsistent condom use (5). MSM in Vietnam have consistently reported low levels of condom use with casual and regular male partners (8, 9).

Amphetamine type stimulants (ATS) are commonly used drugs by MSM, and their use has been found to be associated with condomless anal intercourse (CAI) and HIV infection (12). A recent meta-analysis found a significant association between methamphetamine and amphetamine use and HIV infection across 35 studies (13). However, most previous studies have been conducted in high-income countries, and evidence regarding the association between ATS use and HIV infection among MSM is lacking in low- and middle-income countries (13), particularly Vietnam. It was reported that ATS use, particularly methamphetamine use is prevalent among MSM in Vietnam (14). The relationship between ATS use and HIV infection among MSM in Vietnam, however, remains to be assessed.

In Vietnam, homosexuality remains socially stigmatized (15), despite recent activism to protect the rights of lesbian, gay, bisexual, and transgender people. Previous international research underscores that homosexuality-related stigma and discrimination are associated with a higher risk of depression (16, 17). Depression has been found to be highly prevalent among MSM, particularly HIV-positive men (18, 19), and is considered a major health issue among MSM (20). Furthermore, homosexuality-related stigma, discrimination, and depression have been found to be associated with engaging in HIV-related risky behaviors such as CAI (21–23), drug use (24, 25), having sex while on drugs (26), less awareness and underutilization of HIV prevention services (27–29), and experiencing less benefit from participating in HIV prevention interventions (27).

Previous studies of HIV infection among MSM in Vietnam have mainly focused on individual-level covariates rather than examining social and structural barriers to HIV prevention, such as homosexuality-related stigma and discrimination. Evidence from previous studies indicates that sexual sensation seeking is associated with an increased likelihood of CAI among MSM (30–33) and that sexual sensation seeking can modify or strengthen the association between alcohol or drug use and HIV-related sexual behaviors (34, 35). However, the effect of sexual sensation seeking on HIV risk among MSM in Vietnam has not been previously investigated.

Previous research in Vietnam has found relatively high rates of CAI between MSM (8, 9), and international research has found that MSM may use various strategies to reduce HIV transmission risk during CAI, such as serosorting (having sex with partners of the same perceived HIV status), strategic positioning (HIV-negative men being insertive during CAI), withdrawal before ejaculation, or limiting CAI to HIV-positive partners who are virally suppressed (36, 37). However, belief in the efficacy of these strategies has not been previously assessed among Vietnamese MSM.

To improve HIV prevention among MSM in Vietnam, we sought to assess the prevalence of HIV and undiagnosed infection among MSM in Hanoi and examined factors associated with HIV infection, including homosexuality-related stigma and discrimination, depression, sexual sensation seeking, belief in the efficacy of risk reduction strategies, and drug use, particularly ATS use.

Participants included in this analysis were part of a larger convenience sample of 303 MSM recruited into a cross-sectional, community-based study in Hanoi, Vietnam, from September to October 2014. The study received approval from the Human Research Ethics Committee of the University of New South Wales, Australia, and from the Institutional Review Board of the Hanoi School of Public Health. A description of the study has been previously published (14). In short, the study was conducted in collaboration with the Hanoi Center for HIV/AIDS Prevention and Control (Hanoi PAC), the Center for Community Health Promotion (CHP), and MSM community-based organizations (CBOs). MSM are a relatively hidden population in Vietnam, and developing a randomized sampling frame is impossible. Convenience sampling was hence used to recruit participants. First, staff and outreach workers of collaborating organizations referred potential participants to the study. Additionally, peers of collaborating CBOs referred men from their social networks. Finally, participated men were asked to invite their peers who might be interested in the study.

Men were eligible to participate if they were 18 years or older at the time of the study, reported having anal sex with at least one man in the previous 3 months, had a good command of the Vietnamese language, and provided consent. Men were screened for eligibility and were interviewed after provided written consent. Upon interview completion, men were informed about optional HIV testing.

Men who chose to be tested were referred to an on-site testing team provided by Hanoi PAC. Separate written consent was obtained for HIV testing. Venous blood samples were collected by technicians from Hanoi PAC. Blood samples were assigned a unique, anonymous ID code enabling linkage to participants’ questionnaires (and for participants to get results). Due to resource constraints, we could only offer 210 free HIV tests to participants.

A total of 222 men were referred to the study as potential participants, among whom nine men did not meet selection criteria, two men chose not to complete an interview, and one man refused to be tested. As such, the following analysis includes 210 men who completed an interviewer-administered questionnaire and agreed to be tested for HIV and release their HIV test result. We compared the sociodemographic characteristics of men who did and did not undertake HIV testing (analysis not shown). Men who tested for HIV and consented to release their HIV test results were significantly younger, had lower incomes, and were more likely to be students or self-employed. Men who did and didn’t undertake HIV testing were similar in terms of place of birth, education level, sexual orientation, and perceived HIV status.

To the best of our knowledge, this is the first reported analysis of an association between a broad range of important structural, personal dispositions, and behavioral factors and HIV infection among MSM in Vietnam. While we found that MSM who reported recently using amphetamine or ecstasy before or during sex were not more likely to have an HIV positive test result, MSM who self-reported the recent use of methamphetamine before or during sex had a fivefold increased likelihood of HIV infection, compared with MSM who did not use methamphetamine for sex. These findings are similar to those of a recent meta-analysis (13), as well as recent empirical research, finding higher rates of methamphetamine and/or amphetamine use among diagnosed HIV-positive MSM compared to HIV-negative MSM (44–47). In our study, we also found that men who engaged in recent sex work were more likely to test positive for HIV. Together, our findings suggest that men who use ATS for sex and men who engage in sex work should be targeted as priority groups for HIV prevention in Hanoi, Vietnam. We also suggest that interventions for methamphetamine use are made available for MSM in Vietnam and be incorporated into current HIV prevention activities. Furthermore, future periodic surveillance of HIV among MSM in Vietnam would benefit from the inclusion of measures of ATS use and its association with sexual risk behaviors. Such research would contribute to an increasing understanding of the complex relationships between drug use, sexual behaviors, and HIV infection among Vietnamese MSM that can guide HIV prevention.

We found a relatively moderate prevalence of HIV (6.7%) among MSM recruited in Hanoi, lower than that found in previous government-run surveillance studies (6, 8). Our convenience sample did not include any MSM who reported injecting drug use, so we may have under-recruited men who are at higher risk of HIV. As such, generalizing our findings to the broader community of MSM in Hanoi should therefore be undertaken with caution. Strikingly, we found the majority of HIV-positive men (12 out of 14) indicated that they were HIV-negative or did not know their HIV status. To the best of our knowledge, no previous studies have reported the level of undiagnosed HIV among MSM in Vietnam (7, 9, 11, 48), and our results suggest that many HIV-positive MSM in Hanoi may be unaware of their infection. Some of the HIV-positive men in our study may have chosen not to reveal that they had already been diagnosed when interviewed, because of reticence or fear about disclosing their status. Previous studies in high-income countries, while reporting lower levels of undiagnosed HIV (49, 50), have found that men with undiagnosed HIV report more risky sexual and drug use behaviors than HIV-negative men (49). We also found a borderline association between homosexuality-related perceived stigma and HIV infection in our analysis. Therefore, promoting accessible HIV testing services, for example, MSM-run, community-based, HIV testing services, is recommended, because they could encourage HIV testing as well as returning for HIV test results (51). Additionally, as little is known about undiagnosed HIV among MSM in Vietnam, future research could assess the extent of undiagnosed HIV and its correlates in different parts of the country.

We did not find a significant association between HIV infection and any form of CAI, despite previous research establishing CAI as a key risk factor for HIV infection in MSM (52). Since the sample size for this analysis was relatively small, power may have been insufficient to detect an association between CAI and HIV infection. Alternatively, the lack of variance between HIV status groups may reflect a ceiling effect of high levels of CAI in both HIV-positive and non-HIV-positive MSM. Because CAI with male sexual partners was so common in the sample (73.8%) and the level of undiagnosed HIV was strikingly high, we recommend an intensified promotion of safe sex among MSM in Hanoi.

Previous studies have found that depression can be highly prevalent among MSM and is more likely higher among diagnosed, HIV-positive MSM (41, 53). However, we did not find an association between depression and HIV infection in our sample. This may be because we found a relatively low prevalence of depression in the sample, and the majority of men who had HIV were unaware of their infection. We also did not find an independent association between sexual sensation seeking and HIV infection. However, like other researchers, we have previously found a positive relationship between sexual sensation seeking and CAI (30–33).

Our study had several limitations. Since MSM are a hidden population in Vietnam, we used a convenience sampling approach, as a result of which our findings may not be representative of the broader MSM population in Hanoi. Our sample is more likely to be representative of young MSM in urban settings in Vietnam who are students or self-employed and have lower incomes. As MSM are a hidden population in Vietnam, previous studies have also used a variety of non-random convenience sampling methods and, as in many high income countries, no randomized samples of MSM have been recruited in Vietnam (8, 9, 38, 54–56). Also, although we tried to eliminate reporting bias during the interview process, our findings might reflect underreporting of sexual and drug use behaviors and other socially sensitive issues. Additionally, men who engaged in transactional sex were disproportionately affected by HIV (57). As one fifth of the sample engaged in sex work, assessing sex practices with their sexual partners would have been useful but no such assessment was included in our study.

We found a moderate prevalence of HIV infection among MSM in Hanoi, Vietnam, and most of the men who tested HIV-positive seemed to be unaware of infection. HIV infection was associated with sex-related methamphetamine use and engagement in sex work. Our analytical and descriptive findings point to several recommendations. For HIV prevention, we recommend an integration of interventions for methamphetamine use into HIV prevention, an intensified promotion of safe sex, and implementation of community-based, MSM-run, or MSM-friendly HIV testing services in Hanoi, Vietnam. In research, we recommend the routine assessment of ATS use in national HIV surveillance and research to enable analysis of trends in ATS use and associations with sexual behaviors. We also recommend further study of men’s beliefs and practices with respect to various harm reduction strategies. Finally, we urge examination of the extent of undiagnosed HIV infection in MSM in different parts of Vietnam.

NV led the development of the research protocol and data collection tools, undertook data collection and data analysis, wrote the initial draft of the manuscript, and prepared the final manuscript. JW and MH guided and supervised the development of the research protocol, data collection and analysis, and contributed to the writing of the manuscript. HP, LL, GT, and TD provided advice and guidance on the research protocol and data collection and contributed to the manuscript.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The reviewer ZW and handling Editor declared their shared affiliation, and the handling Editor states that the process nevertheless met the standards of a fair and objective review.