Groundbreaking research reveals that nearly one-third of participants in Hanoi's HIV PrEP program have asymptomatic chlamydia or gonorrhea infections
Imagine a health program so effective that it reduces the risk of HIV infection by over 99%. Now imagine that within this same program, doctors discover an invisible epidemic affecting nearly one-third of participants. This isn't a hypothetical scenario—it's exactly what researchers found in an HIV prevention program in Hanoi, Vietnam. A groundbreaking study revealed that while participants were successfully protected from HIV, they were simultaneously experiencing alarmingly high rates of two other sexually transmitted infections: chlamydia and gonorrhea 1 5 .
This surprising discovery highlights a critical gap in our approach to sexual health. Even as we make tremendous strides against one virus, other bacterial infections continue to spread, often without any symptoms. The Hanoi study provides crucial insights that could reshape how we approach sexual healthcare in resource-limited settings worldwide, emphasizing that protecting health requires addressing multiple threats simultaneously 5 8 .
Chlamydia and gonorrhea are among the world's most common sexually transmitted infections. Both are caused by bacteria—Chlamydia trachomatis and Neisseria gonorrhoeae, respectively—that can be transmitted through vaginal, anal, or oral sex 3 9 .
What makes these infections particularly deceptive is their silent nature. Most people infected with chlamydia or gonorrhea experience no symptoms at all, unknowingly spreading the infections to others. When symptoms do occur, they might include:
The World Health Organization estimates that in 2020 alone, there were approximately 128.5 million new chlamydia infections and 82.4 million new gonorrhea infections among adults aged 15-49 worldwide 3 9 . These infections are more than just temporary inconveniences—they can cause serious long-term health consequences, including pelvic inflammatory disease, ectopic pregnancy, and infertility in women, and similar reproductive complications in men 3 9 .
Perhaps most concerning is the powerful synergy between STIs and HIV. Having chlamydia or gonorrhea significantly increases both the risk of acquiring HIV if exposed, and the risk of transmitting HIV to others 3 . This interconnection explains why STI screening has become a standard component of comprehensive HIV prevention programs like PrEP (pre-exposure prophylaxis).
Between January and December 2022, researchers conducted an observational study at the Sexual Health and Promotion Clinic at Hanoi Medical University 5 8 . They enrolled 529 participants who were all male at birth, aged 16 or older, had at least one male sex partner in the previous year, and were enrolled in the HIV PrEP program 1 5 .
The research methodology was thorough:
Study participants
All enrolled in Hanoi's HIV PrEP programThe results were striking. The overall prevalence of either chlamydia or gonorrhea was 28.9%—meaning nearly one in three participants had at least one of these infections 1 5 .
When researchers looked closer, they discovered that these infections weren't distributed evenly across anatomical sites, and the patterns differed between the two infections:
| Infection Type | Overall Prevalence | Urethral Prevalence | Rectal Prevalence | Pharyngeal Prevalence |
|---|---|---|---|---|
| Any CT or NG | 28.9% (153/529) | Not reported | Not reported | Not reported |
| Chlamydia (CT) | 20.4% (108/529) | Not reported | 15.0% (74/493) | Not reported |
| Gonorrhea (NG) | 14.4% (76/529) | Not reported | Not reported | 11.7% (62/528) |
Table 1: Infection Prevalence by Anatomical Site
Perhaps the most notable finding was that more than half (54.2%) of those with infections reported no symptoms in the previous week 1 5 . This underscores the silent nature of these epidemics and explains why they can spread undetected through populations.
The data also revealed another critical insight: among asymptomatic participants, urethral infections were relatively uncommon, with only 3.1% having urethral chlamydia and 0.9% having urethral gonorrhea 1 5 . This suggests that focusing screening only on the urethra would miss the majority of infections.
Through detailed statistical analysis, the research team identified two key factors associated with higher infection rates:
These findings help identify which individuals might benefit most from targeted screening and prevention efforts.
| Research Material | Function in the Study |
|---|---|
| Alinity m Multi-Collect Specimen Collection Kits | Standardized collection of urine, rectal, and pharyngeal specimens |
| cobas PCR Urine/Swab Sample Kits | Alternative collection system for patient samples |
| Alinity m STI Assay | Molecular testing to detect chlamydia and gonorrhea genetic material |
| cobas 4800 CT/NG Assay | Advanced molecular testing platform for accurate detection |
| Self-administered tablet survey | Collected demographic, behavioral, and clinical data confidentially |
Table 2: Key Research Materials and Their Functions
The study employed molecular testing methods, specifically nucleic acid amplification tests (NAATs), which represent the gold standard for detecting chlamydia and gonorrhea 5 9 . These sophisticated tests work by amplifying and identifying unique genetic sequences of each bacterium, making them extremely sensitive—capable of detecting even small numbers of bacteria present.
The research team also implemented multivariate logistic regression, a statistical technique that allowed them to identify which factors were independently associated with infection risk while controlling for other variables 5 . This is how they determined the significant role of condomless sex and sexualized drug use.
The Hanoi study challenges conventional approaches to STI screening in several important ways:
The finding that most infections were extragenital (located in the rectum or throat) rather than urethral suggests that urine-only testing would miss the majority of cases. This has significant implications for clinical practice, particularly in resource-limited settings where testing capabilities may be constrained 1 5 .
The patterns observed in Hanoi align with research from other regions. In the United States, the CDC recommends routine multi-site STI screening for men who have sex with men, particularly those on PrEP 4 . The high STI rates among PrEP users have been documented in various settings, likely reflecting both higher-risk sexual behaviors and more frequent testing 5 .
| Population Group | Chlamydia Prevalence | Gonorrhea Prevalence | Source/Region |
|---|---|---|---|
| MSM in Hanoi PrEP Program | 20.4% | 14.4% | Vietnam Study 1 |
| Pregnant Women (Global) | 8.4% | Not reported | Global Meta-Analysis 6 |
| General Population (Southeast Asia) | Not reported | 0.5% | Regional Review |
| STI Clinic Attendees (Southeast Asia) | Not reported | 16.8% | Regional Review |
Table 3: Global Chlamydia and Gonorrhea Prevalence in Different Populations
For low- and middle-income countries, the study presents both a challenge and an opportunity. The researchers noted that in Vietnam's PrEP program, clients typically bear the costs of chlamydia and gonorrhea testing themselves, which limits testing uptake 5 . The findings suggest a need to reconsider how limited healthcare resources are allocated for STI prevention.
Rather than universal multi-site testing, the identification of specific risk factors could enable more targeted and cost-effective approaches. For instance, focusing on individuals who report condomless sex or sexualized drug use might maximize the impact of limited testing resources 1 5 .
The Hanoi PrEP study reveals a critical paradox in sexual health: the very individuals who are most proactive about their health—by seeking HIV prevention services—may still be vulnerable to other silent infections. The 28.9% prevalence rate of chlamydia or gonorrhea found in the study is not just a statistic; it represents a substantial population unknowingly living with and potentially transmitting these infections 1 5 .
This research demonstrates that comprehensive sexual health requires looking beyond a single infection, even one as serious as HIV. The findings make a powerful case for integrating routine multi-site STI screening into HIV prevention programs, particularly for those with identified risk factors 8 .
As we continue to make progress against HIV, studies like this one remind us that sexual health is multidimensional. Addressing the silent epidemics of chlamydia and gonorrhea, especially in populations vulnerable to HIV, represents an essential next frontier in our pursuit of better sexual health for all. The insights from Hanoi light the path forward—not just for Vietnam, but for similar settings worldwide where resources must be deployed wisely for maximum impact.